Buddhism is the largest-religion in Thailand, followed by around 92.5% of the country's population as per 2021. By sheer numbers, it has the world's largest Buddhist population followed by China and Myanmar, with more than 67 million Buddhists. The Theravada branch is practiced by most Buddhists and shares many similarities with Sri Lankan Buddhism. Buddhism in Thailand has also become integrated with Hinduism from millennia of Indian influence, and Chinese religions from the large Thai Chinese population.'Lamphun's Little-Known Animal Shrines' in: Forbes, Andrew, and Henley, David, Ancient Chiang Mai Volume 1. Chiang Mai, Cognoscenti Books, 2012. Buddhist temples in Thailand are characterized by tall golden stupas, and the Buddhist architecture of Thailand is similar to that in other Southeast Asian countries, particularly Cambodia and Laos, with which Thailand shares cultural and historical heritages. Thailand, Cambodia, Myanmar, Sri Lanka and Laos are countries with Theravada Buddhist majorities.
Buddhism is believed to have come to what is now Thailand as early as the 3rd century BCE, in the time of the Indian Emperor Ashoka. Since then, Buddhism has played a significant role in Thai culture and society. Buddhism and the Thai monarchy have often been intertwined, with Thai kings historically seen as the main patrons of Buddhism in Thailand. Although politics and religion were generally separated for most of Thai history, Buddhism's connection to the Thai state would increase in the middle of the 19th century following the reforms of King Mongkut that would lead to the development of a royally-backed sect of Buddhism and increased centralization of the Thai sangha under the state, with state control over Buddhism increasing further after the 2014 coup d'état.
Thai Buddhism is distinguished for its emphasis on short-term ordination for every Thai man and its close interconnection with the Thai state and Thai culture. The two official branches, or Nikayas, of Thai Buddhism are the royally backed Dhammayuttika Nikaya and the larger Maha Nikaya.
Pre-modern History
Buddhism in the pre-Thai kingdoms
The Mahāvaṃsa, a historical chronicle of Sri Lanka, mentions that during the reign of Ashoka (c. 268 to 232 BCE), monks Sona Thera and Uttara Thera were sent to spread Buddhism to Suvannabhumi, which is somewhere in Southeast Asia.Modi's Bangkok visit: India-Thailand friendship is heading for a strategic upgrade, The Print, 1 April 2025.Upendra Thakur (1986). Some Aspects of Asian History and Culture, pp. 149-150. Abhinav Publications. Thai scholars believe that the Mon kingdom of Dvaravati (c. 6th to the 11th century) is likely to have received Buddhist missionaries during this era. This is because numerous archeological finds in the ancient Dvaravati cities like Nakon Pathom point to an early Buddhist presence. These finds include Dharma wheels, Buddha footprints, crouching deer and Pali inscriptions.Jermsawatdi, Promsak (1979). Thai Art with Indian Influences, p. 22. Abhinav Publications Thus, Dvaravati Buddhism was probably an Indian form of Theravada (or at least a non-Mahayana) Buddhism.Jermsawatdi, Promsak (1979). Thai Art with Indian Influences, p. 23. Abhinav Publications The Dvaravati style has been compared to the Amaravati style and may be influenced by it.Patit Paban Mishra (2010). The History of Thailand, p. 33. Greenwood History of Modern Nations Series. It has been suggested that the original structure of the ancient Phra Pathom Stupa (which has been covered by restorations and a spire that was added later) was of similar design to the Stupa of Sanchi.Jermsawatdi, Promsak (1979). Thai Art with Indian Influences, pp. 21-22. Abhinav Publications
Later finds at Nakon Pathom and nearby cities also include Buddha images in the Gupta style. The spread of Buddhism in Southeast Asia may have arrived with merchant ships traveling the key maritime trade routes with India.Patit Paban Mishra (2010). The History of Thailand, pp. 30-32. Greenwood History of Modern Nations Series.
Various Southeast Asian kingdoms that ruled over parts of modern Thailand, such as the Khmer Empire (c. 802–1431 CE) and the Mon Lavo Kingdom (c. 450–1388 CE), were influenced by Indian Buddhist trends, which included Mahāyāna Buddhism and the Sanskrit Buddhist tradition.Upendra Thakur (1986). Some Aspects of Asian History and Culture, pp. 150-51. Abhinav Publications.
The Mon Kingdom of Hariphunchai with its capital at Lamphun was also a Buddhist realm, with famous temples like Wat Haripunchai (1040) and Wat Chamadevi (1218).Patit Paban Mishra (2010). The History of Thailand, p. 25. Greenwood History of Modern Nations Series.
The religious arts of the Indonesian Kingdom of Srivijaya (c. 650–1377), which controlled part of Southern Thailand, depict numerous figures from Indian Mahāyāna. Archeological finds in Southern Thailand (such as at Phra Phim and Nakon Sri Thammaraj) attest to the practice of Mahāyāna Buddhism in this region.
Starting at around the 11th century, Sinhalese Theravada monks gradually led the conversion of most of Southeast Asia to the Sinhalese Mahavihara sect of Theravāda. This was supported by powerful Southeast Asian kings, such as the Burmese Anawratha (1044–1077), who promoted Theravada throughout the Bagan Kingdom, which included parts of Thailand that he conquered.Upendra Thakur (1986). Some Aspects of Asian History and Culture, pp. 151. Abhinav Publications.
The first Thai states: Sukhothai and Lan Na
Beginning in the 7th century, Thai people gradually migrated from China to Southeast Asia. They eventually began conquering Southeast Asian kingdoms like Hariphunchai and adopting the practice of Buddhism which had existed in the conquered regions. The first ethnic Thai kingdom was the Sukhothai Kingdom (13th-15th century), which was founded in 1238.Patit Paban Mishra (2010). The History of Thailand, p. 36. Greenwood History of Modern Nations Series. At first, both Theravāda and Mahāyāna were practiced in this new Thai realm, as well as Khmer Brahmanism.Prapod Assavavirulhakarn. The Ascendancy of Theravada Buddhism in Southeast Asia. Chiang Mai: Silkworm Books, 2010.Upendra Thakur (1986). Some Aspects of Asian History and Culture, p. 152. Abhinav Publications.
During the 13th century, Thai monks traveled to Sri Lanka to ordain in the Sinhalese Mahavihara Theravada sect (known as Lankavamsa/Lankavong in Thailand) lineage and to study the teachings. Lankavong monks also traveled to Thailand to teach Theravada Buddhism. Archeological evidence suggests that the most active region for the initial spread of Sinhalese Theravada was at Nakon Sri Thammarath (in South Thailand).Yoneo Ishii (1986). Sangha, State, and Society: Thai Buddhism in History, p. 60. University of Hawaii Press.
King Ram Khamhaeng ( late 13th century) gave royal support to the Lankavong Theravāda monks in Nakon Sri Thammarath. He invited them to his capital, built monasteries for them, and subsequently sent more monks to Sri Lanka to study.Patit Paban Mishra (2010). The History of Thailand, p. 37-38. Greenwood History of Modern Nations Series.Jermsawatdi, Promsak (1979). Thai Art with Indian Influences, p. 33. Abhinav Publications This royal support increased the prestige and influence of Theravāda in Thailand. During Ram Khamhaeng's reign, stupas were built, reflecting the Sri Lankan influence. One of these is Wat Chang Lom. Thai travelers to Sri Lanka also brought back the root of a Bodhi tree, under which the Buddha attained enlightenment, which began the Thai tradition of venerating Bodhi trees. Sukhothai style Buddha statues also reflect Sri Lankan art styles.Jermsawatdi, Promsak (1979). Thai Art with Indian Influences, p. 34. Abhinav Publications
Under the reign of Ram Khamhaeng, the position of sangharaja (leader of the monastic community) was created and tasked with the administration of the sangha, the orders of monks and nuns. Other monks were also given lower-level administrative positions.Jermsawatdi, Promsak (1979). Thai Art with Indian Influences, pp. 34-35. Abhinav Publications
Later Sukhothai kings would continue this policy of supporting Lankavong Theravāda, and numerous monasteries, Buddha images and stupas were built during the Sukhothai period. The study of Pali Buddhist texts was also promoted. Thai kings also inherited the concept of Buddhist kingship from the tradition. This was based on the idea that the Buddhist "Dhamma king" ruled in conformity with the Dhamma (the universal law and the Buddha's teaching which points to it), particularly the ten kingly virtues mentioned in the Aggañña Sutta, which include giving alms, morality, liberality, gentleness, non-anger, and non-harming.Yoneo Ishii (1986). Sangha, State, and Society: Thai Buddhism in History, pp. 150-151. University of Hawaii Press.
Mahathammaracha I (r. 1346–1368) was a Sukhothai king known as a great scholar and patron of Buddhism, who even became a monk for a brief period of four months. A treatise on Buddhist cosmology, the Tribhumikatha (Trai Phum Phra Ruang, "The Three Worlds According to King Ruang"), has been attributed to him, and is one of the oldest traditional works of Thai literature.Patit Paban Mishra (2010). The History of Thailand, p. 38. Greenwood History of Modern Nations Series. During the reign of Mahathammaracha I, another group of monks arrived from Sri Lanka, led by Somdet Phra Mahasami (Sumana), who was associated with a Sri Lankan forest monastery named Udumbaragiri.Tambiah, Stanley Jeyaraja (1984). The Buddhist Saints of the Forest and the Cult of Amulets, p. 66. Cambridge University Press.
Further north, in the Thai Lan Na Kingdom (c. 1292–1775), Theravāda also flourished. Lan Na kings built unique wats (monasteries) which show a blend of Mon, Indian, Burmese and Khmer styles. Some important early Lan Na wats include Wat Ku Kham (Temple of the Golden Chedi, c. 1288) and Wat Chiang Man (c. 1297) both built by the first Lan Na king Mangrai (1238–1311).
King Pha Yu (r. 1345–1367), continued promoting Buddhism. He shifted the capital to Chiang Mai and built Wat Li Chiang. His successor, Keu Na (1367–1385), invited the forest monk Somdet Phra Mahasami to Lan Na to introduce his Sri Lankan forest sect. Mahasami arrived with relics which were enshrined at the newly built Wat Suan Dauk. This wat became the headquarters of the Sri Lankan forest sect.Tambiah, Stanley Jeyaraja (1984). The Buddhist Saints of the Forest and the Cult of Amulets, p. 67. Cambridge University Press. Wat Phra Singh (c. 1385) is another example of classic Buddhist architecture of the Lan Na kingdom.
In the reign of Sam Fang Kaen (1411–1442), a controversy broke out between the Sri Lankan sect of Somdet Phra Mahasami and another Sri Lankan order newly arrived from Ayutthya, which criticized the old order for accepting money and owning rice lands.
Sam Fang Kaen was deposed by Tilokaraj (r. 1441–1487), who placed his support behind the new, more rigorous forest sect and allowed it to become the dominant sect in the kingdom. He is known for building several monasteries for the new Buddhist order, including Wat Chet Yot and Wat Pa Daeng. The king also enlarged Wat Chedi Luang to house the Emerald Buddha.Ongsakul, Sarassawadee (2005). History of Lan Na, pp. 77-81. Chiang Mai: Silkworm Books. . During his reign, in c. 1477, a Buddhist council convened to review the Pali Canon. It is considered the eighth Buddhist council in the Thai tradition.Patit Paban Mishra (2010). The History of Thailand, p. 42. Greenwood History of Modern Nations Series.