Thailand, officially the Kingdom of Thailand, and formerly known as Siam, is a country located in Mainland Southeast Asia. It shares land borders with Myanmar to the west and northwest, Laos to the east and northeast, Cambodia to the southeast, and Malaysia to the south. Its maritime boundaries include the Gulf of Thailand and the Andaman Sea, and it shares maritime borders with Vietnam, Indonesia, and India. Thailand has a population of nearly 66 million people and covers an area of approximately 513,115 km2 (198,115 sq mi). The capital and largest city is Bangkok.
Archaeological evidence indicates that humans have inhabited the area for at least 40,000 years. Indigenous ethnic groups include the Mon, Khmer, and Malay people. The Tai people are believed to have originated from the Điện Biên Phủ region since the 5th century and began migrating into the territory of modern Thailand between the 8th and 10th centuries. During the classical historical period, major kingdoms such as Sukhothai, Lan Na, and Ayutthaya were established. The Sukhothai Kingdom is regarded as the beginning of Thai history, while the Ayutthaya Kingdom, founded in 1350 CE, became a regional power replacing the Khmer Empire. European contact began in 1511 when Portuguese envoys arrived in Ayutthaya. The Ayutthaya Kingdom flourished until its complete destruction during the 1765–1767 Burmese–Siamese War by the Burmese forces under the Konbaung dynasty in 1767.
After the fall of Ayutthaya, King Taksin reunified the kingdom and established the Thonburi Kingdom, which lasted only 15 years before he was overthrown by Phutthayotfa Chulalok (Rama I), the founder of the Chakri dynasty. King Rama I established the Rattanakosin Kingdom and moved the capital to Bangkok in 1782. During the era of Western imperialism, Siam remained the only country in Southeast Asia to avoid colonisation by European powers, although it ceded territory, trade rights, and legal privileges through several unequal treaties. The governance system evolved into an absolute monarchy centralised under the rule of King Chulalongkorn (Rama V). Siam adapted to international relations during the imperialist era and joined World War I on the side of the Allies, a political decision aimed at revising the effects of unequal treaties and enhancing Siam's international status.
Following the Siamese revolution of 1932 by the Khana Ratsadon (lit. 'People's Party'), Siam transitioned to a parliamentary constitutional monarchy and was officially renamed Thailand. During World War II, the country was under the military dictatorship of Plaek Phibunsongkhram and allied with the Empire of Japan as part of the Axis powers, but Thailand did not become a defeated nation due to the underground Free Thai Movement's "Declaration of Peace", which was recognised by the Allies. During the Cold War, Thailand became a key major non-NATO ally of the United States and played a major role in countering communism in the Korean War, the Vietnam War, and other proxy wars. Thailand also joined the Southeast Asia Treaty Organization (SEATO). In the 1970s through 1990s, Thailand alternated between liberal democracy and military dictatorship.
In the 21st century, Thailand has experienced political conflict between supporters and opponents of Prime Minister Thaksin Shinawatra, leading to the 2006 and 2014 coups d'état. Thailand operates under the 2017 Constitution and a coalition government following the 2019 Thai general election, as well as political demonstrations demanding democracy and monarchy reform. The current constitutional structure allows de facto political influence by the Royal Thai Armed Forces. Thailand has faced border tensions from the 2008–2011 Cambodian–Thai border crisis extending to the 2025 Cambodian–Thai border crisis involving territorial disputes and military clashes.
Thailand is recognised as a developing country and holds significant geopolitical importance as a regional power in Southeast Asia. A unitary state governed under a parliamentary system, Thailand promotes its shared values and interests through participation in international organisations including the United Nations and the Association of Southeast Asian Nations (ASEAN), and as a major non-NATO ally of the United States. As a newly industrialised country, its economy ranks among the largest in the region, relying chiefly upon manufacturing, agriculture, and tourism.
Etymology
Before 1939, Thailand was known internationally as Siam. The word Thai (ไทย) is traditionally interpreted to mean 'free man' in the Thai language, distinguishing the Thai from serfs in historical society. However, other scholars suggest the term originally meant simply 'people' or 'human being', noting its historical use in rural areas.
Thais typically refer to their country using the polite form prathet Thai (Thai: ประเทศไทย) or the more colloquial mueang Thai (Thai: เมืองไทย). The word mueang, which archaically referred to a city-state, is commonly used to denote a city or region. The country's official name, Ratcha-anachak Thai (Thai: ราชอาณาจักรไทย), translates to 'Kingdom of Thailand'. Etymologically, its components derive from Sanskrit and Pali: ratcha ('royal'), ana ('authority'), and -chak ('wheel', a symbol of power).
The former name Siam may have originated from the Sanskrit word śyāma (श्याम, 'dark') or the Mon word rhmañña ('stranger'), which likely shares a root with Shan and Assam. Another theory suggests the name derives from the Chinese term Xiān, used to refer to the region. Following the merger of local kingdoms in 1349, Chinese records began referring to the Ayutthaya Kingdom as Xiānluó (暹羅). The ancient Khmers also used Siam to refer to the people settled in the Chao Phraya River valley, as recorded in 13th-century inscriptions.
The name Siam gained official status in international relations during the 19th century, notably appearing in the Bowring Treaty under the signature of King Mongkut (r. 1851–1868), who signed as Mongkut Rex Siamensium (Mongkut, King of the Siamese). Following the transition to a constitutional monarchy, the country was officially renamed Thailand on 24 June 1939.
History
Prehistory and origins
Continuous human habitation in present-day Thailand dates back at least 20,000 years. Agriculture emerged with rice cultivation around 2000 BCE, alongside participation in the Maritime Jade Road, a trading network connecting Southeast Asia from 2000 BCE to 1000 CE. The Ban Chiang site in northeast Thailand is the earliest known centre of copper and bronze production in Southeast Asia, dating between 2000 and 1000 BCE. Iron working appeared around 500 BCE.
The Indochinese Peninsula was heavily influenced by the culture and religions of India from the time of Funan, established in the 2nd century BCE. By the 6th century, early multiethnic kingdoms emerged, including the Mon principalities of Dvaravati and Hariphunchai. In the 9th century, the Khmer people established the Khmer Empire, centred in Angkor, while Tambralinga, a Malay state, rose to control trade through the Strait of Malacca in the 10th century.
The Thai people belong to the Tai ethnolinguistic group. While their exact origins are debated, historians suggest their ancestors migrated from southern China and northern Vietnam into present-day Thailand between the 6th and 11th centuries. Migrating into territory occupied by Mon and Khmer populations, the Tai intermixed with local groups and absorbed Indian, Mon, and Khmer cultural influences. Modern studies indicate that "Thai" serves more as a cultural designation resulting from this integration rather than a distinct genetic ethnicity.
The term Syam first appears in the 11th and 12th centuries in Champa epigraphy and the bas-reliefs of Angkor Wat, which depict warriors and prisoners of war. Pre-14th-century Mainland Southeast Asian sources primarily used Syam as an ethnonym for a cultural group distinct from the Khmer, Cham, Mon, or Bagan. Chinese sources used Xian as a toponym for the region.
Early Tai confederate cities (673 BCE – 13th century CE)
Ancestors of the Tai-speaking peoples are believed to have originated in the Yangtze basin as early as the 12th century BCE. Following conflicts with Chinese expansion in Guangxi, Tai groups gradually migrated southwestwards along rivers and mountain passes into Southeast Asia. By the first millennium CE, they had established early city-states across present-day northern Thailand, Laos, and northeastern Myanmar, becoming a dominant regional power.
According to northern chronicles, early Tai confederacies like Singhanavati and its successor Ngoenyang were established in northern Thailand during the first millennium CE. In 1262, King Mangrai relocated the Ngoenyang capital to Chiang Mai, founding the Lan Na kingdom. Mangrai unified surrounding principalities and expanded southwards, annexing the Mon kingdom of Hariphunchai in 1292.
Further south, Tai migrants interacted with indigenous Khmer and Mon populations through conflict and royal intermarriage. By the 12th century, Tai leaders controlled cities in the upper Chao Phraya basin. Their gradual displacement of Khmer and Mon influence culminated in the establishment of the Sukhothai Kingdom in 1238, marking a major shift in the region's political landscape.
Dvaravati (7th–11th centuries)
The Chao Phraya River was home to the Mon Dvaravati culture, which flourished from the 7th to the 11th century. Samuel Beal identified the polity in Chinese records as "Duoluobodi". Early 20th-century excavations established Nakhon Pathom Province and U Thong as major centres. Dvaravati inscriptions used Sanskrit and Mon written in scripts derived from the Pallava alphabet.
Dvaravati is associated with Theravada Buddhism, likely transmitted from Sri Lanka, while its ruling class participated in Hindu rites. Dvaravati art shows strong Indian influence, whereas the eastern Chao Phraya valley displays greater Khmer and Hindu influence. Dvaravati culture spread into Isan and southwards to the Kra Isthmus. It operated as a network of city-states linked through the mandala political model. Baker and Pasuk challenge the idea that the plain was incorporated into a unified Lavo-Khmer polity, citing the absence of Angkorian temple-endowment inscriptions.
The name Dvaravati derives from medallions bearing the Sanskrit phrase śrīdvāravatīśvarapuṇya found at Nakhon Pathom and other sites. Chinese and Annamese records mention To-lo-po-ti, with tribute missions reaching the Tang court in 638, 640 and 649.
Art historians later extended the term Dvaravati to describe a wider body of styles and their corresponding period. Baker and Pasuk argue these styles spread through trade rather than political authority. Between the 6th and 12th centuries, forty moated towns shared religious practices, artistic traditions and Mon inscriptions but showed little political integration.
Recent research places the coastline near its present position by about 500 CE, challenging older views of a submerged lower gulf. The religious landscape was also diverse; images of Avalokiteśvara and Prajñāpāramitā appeared alongside Buddha images, reflecting mixed Buddhist practices rather than strict divisions.
Lavo
Lavo belonged to the Dvaravati sphere early in the period. Chronicle traditions claim Lavapura was founded in 648—or possibly 538—by Kalavarnadisharaja. The only attested native language is Old Mon. Baker and Pasuk identify Lopburi as Lavapura.
Around the 10th century, central plain city-states reorganised into two mandalas: Lavo in the east and Suvarnabhumi (modern Suphan Buri) in the west. According to Northern Chronicles, a king of Tambralinga installed a Malay prince in Lavo in 903 or 927. This prince married a Khmer princess, and their son became Suryavarman I, linking Lavo to Khmer domination. However, Baker and Pasuk argue Angkorian control of Lavo was asserted rather than demonstrated, and the relationship remained flexible.
Angkor lost Lavo to Suphannabhum princes in 1052, moving the seat to Ayodhya under Narai I. Angkor pushed to recover influence in 1181 when Jayavarman VII appointed a kinsman to govern Lavapura. This pressured Lavo ruler Sri Dharmasokaraja II to flee to Nakhon Si Thammarat. Lavapura was likely recovered in the 13th century by a Tai prince. Angkorian power eventually waned, and in 1238, Bang Klang Hao took Sukhothai from Khom Sabat Khlon Lamphong, conventionally marking the kingdom's foundation.
Siam people
Early references to the Siam people occur in pre-Angkorian inscriptions. A 661 inscription from Angkor Borei mentions a female slave named Ku Sayam, while a 682 inscription records a noble named Sayam. Tatsuo Hoshino identifies several polities in Tang annals as early Tai or Siamese states linking Champa with the Chao Phraya basin. Hiram Woodward considers this linguistic argument tendentious.
Song period Chinese sources describe Xiān guó (暹國) in the western Chao Phraya region, while the east was associated with Lavo. By the 13th and 14th centuries, Siamese polities like Phrip Phri, Suphan Buri, Ayodhya and Sukhothai appeared independently in Chinese records. Evidence for relations with Chenla appears in the Wat Kud Tae inscription, recording a royal marriage. A Champa inscription records Siamese and Angkorian forces attacking Vijaya in 1201. Zhou Daguan reported Siamese influence over Lavapura and their presence in Yaśodharapura.
Xiān and Chen Li Fu (12th–14th centuries)
Before Xiān, Chinese records describe Chên Li Fu, a polity west of Chenla. It sent embassies to the Song court in the early 1200s. Its ruler, Sri Mahidharavarman, bore the Khmer title kamrateng. Its tribute included elephants, ivory, and rhinoceros horn, but the Song court instructed Chên Li Fu to send no further tribute due to distance.
The earliest notices of Xiān are Vietnamese, detailing merchant ships from Xiān reaching Hǎidōng (海東) in 1149. Xiān sent tribute in 1182, and merchants returned in 1241. Chinese records use Xiān for polities of the lower Chao Phraya, which Yoneo Ishii interpreted as several port polities rather than a single state. Xiān first appears in the Chinese record in 1282 or 1283 and sent tribute missions frequently between 1292 and 1323. Lavo, Suphan Buri, Ayodhya and Phetchaburi each dealt with China in its own name before the union of 1349.
The Yuan court's dealings with Xiān indicate a negotiated relationship. Envoys sent to demand submission in 1293 were refused, and the king came in person with tribute in 1295. An edict of 1295 ordered Xiān not to harm Ma-li-yu-er (Melayu), with whom it had long been at war. The older identification of Xiān with Sukhothai was challenged in 1989 by Yamamoto Tatsurō, who noted that a gazetteer places Sukhothai under Xiān and therefore distinguishes the two.
Sukhothai Kingdom (1238–1438)
After the decline of the Khmer Empire and Kingdom of Pagan in the early 13th century, Tai domains stretched from present-day India to the Malay Peninsula. During the 13th century, Tai people settled in the core lands of Dvaravati and Lavo down to Nakhon Si Thammarat.
In 1238, Pho Khun Bang Klang Hao rallied local populations to rebel against the Khmer, crowning himself the first king of the Sukhothai Kingdom. Thai historians count Sukhothai as the first kingdom of the Thai people. It expanded furthest under Ram Khamhaeng, functioning mostly as a network of local lords rather than a tightly controlled empire. He is believed to have invented the Thai script. Sukhothai embraced Theravada Buddhism under Maha Thammaracha I.
Ayutthaya Kingdom (1351–1767)
The Ayutthaya Kingdom rose from the earlier Lavo Kingdom and Suphannaphum with Uthong as its first king. Ayutthaya was a patchwork of self-governing principalities and tributary provinces under the mandala system. Its initial expansion was achieved through conquest and political marriage.
Before the end of the 15th century, Ayutthaya invaded the Khmer Empire three times, sacking its capital Angkor. This marked a major geopolitical shift, allowing Ayutthaya to eclipse the Khmer Empire in mainland Southeast Asia. Sukhothai was steadily incorporated into the kingdom through dynastic marriages. King Borommatrailokkanat brought about bureaucratic reforms and created the sakdina social hierarchy, instituting male corvée labour.