The Dhammayuttika Nikaya or Thammayut Nikaya (Thai: ธรรมยุติกนิกาย, ธรรมยุต; Khmer: ធម្មយុត្តិក និកាយ) is an order of Theravada Buddhist monks in Thailand and Cambodia. Its name is derived from the Pali dhamma ("teachings of the Buddha") + yutti (in accordance with) + ka (group).
Founding in Thailand 
The Dhammayuttika Nikaya, or simply Thammayut, began in 1833 as a reform movement led by Prince Mongkut, a son of King Rama II. Thammayut remained a reform movement until passage of the Sangha Act of 1902, which formally recognized it as the lesser of Thailand's two Theravada denominations.
Prince Mongkut was a bhikkhu (ordination name: Vajirañāṇo) for 27 years (1824–1851) before becoming the King of Siam (1851–1868). In 1836 he became the first abbot of Wat Bowonniwet. After the then 20-year-old prince entered monastic life in 1824, he noticed what he saw as serious discrepancies between the rules given in the Pali Canon and the actual practices of Thai monks, and sought to upgrade monastic discipline to make it more orthodox. Mongkut also made an effort to remove all non-Buddhist, folk religious, and superstitious elements which over the years had become part of Thai Buddhism. Thammayut monks were expected to eat only one meal a day (not two) and the meal was to be gathered during a traditional alms round.
The Thammayut Nikaya has produced two particularly highly revered forest monks: Phra Ajahn Sao Kantasilo Mahathera (1861–1941) and Phra Ajahn Mun Bhuridatta (1870–1949). After their cremations, the bone fragments were distributed to various people and Thai provinces and have since, according to their followers, transformed into crystal-like relics (Pali: śarīra-dhātu) in various hues of translucency and opacity.
Dhammayuttika Nikaya in Cambodia 
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In 1855, the Khmer King Norodom invited Preah Saukonn Pan, also referred to as Maha Pan, a Khmer monk educated in the order of Thailand's now King Mongkut, to establish a branch of the Dhammayuttika order in Cambodia. Maha Pan became the first Supreme Patriarch of the Cambodian Dhammayuttika lineage, residing at Wat Botum Vaddey, a new temple erected by the king specifically for the Dhammayuttika monks. The Dhammayuttika Nikaya in Cambodia benefited from royal patronage, but it was also sometimes regarded with suspicion due to its ties to the Thai monarchy.
The Dhammayuttika order in Cambodia suffered greatly under the Khmer Rouge, being particularly targeted because to its perceived ties to monarchy and a foreign nation, in addition to the Khmer Rouge's general repression of the Buddhist hierarchy in Cambodia. Between 1981 and 1991, the Dhammayuttika Nikaya was combined with the Cambodian Mohanikay in a unified sangha system established under Vietnamese domination. In 1991 King Sihanouk returned from exile and appointed the first new Dhammayuttika sangharaja in ten years, effectively ending the policy of official unification. The Dhammayuttika continues to exist in Cambodia, though its monks constitute a very small minority. On issues such as the role of monks in HIV/AIDS treatment and education, the current sangharaja, Bour Kry has adopted a more liberal position than the Mohanikay head Tep Vong, but is less radical than that of certain Engaged Buddhist elements of the Mohanikay order.
See also 
- Buddhism in Contemporary Thailand, Prof. Phra Thepsophon Ractor Mahachulalongkornrajavidyalaya Speech at the International Conference on Buddhasasana in theravada Buddhist countries: Issue and the way Forward in Colombo, Sri Lanka, January 15, 2003, Buddhism in Thailand, Dhammathai - Buddhist Information Network
- Ratanakosin Period, Buddhism in Thailand, Dhammathai - Buddhist Information Network
- (Harris 2001, p. 83)
- (Keyes 1994)
- (Harris 2001, p. 84)
- (Harris 2001, p. 75)
- (Harris 2001, p. 87)
- Harris, Ian (August 2001), "Sangha Groupings in Cambodia", Buddhist Studies Review (UK Association for Buddhist Studies) 18 (I): 65–72
- Keyes, Charles F. (1994), "Communist Revolution and the Buddhist Past in Cambodia", Asian Visions of Authority: Religion and the Modern States of East and Southeast Asia, Honolulu, HI: University of Hawai`i Press, pp. 43–73
- Thai Forest Tradition
- Thudong Tradition
- Forest Sangha
- Ajaan Mun Relics
- History of the Movement by Thanissaro Bhikkhu