Theravāda

Missionaries carried Theravāda to Sri Lanka under Ashoka. Its scriptures, the Pāli Canon, were written down in the first century BCE and are its sole authority.

In the eleventh century Sinhalese monks and Southeast Asian rulers began converting the mainland. Anawrahta of Pagan (1044–1077) and Ram Khamhaeng of Sukhothai in the late thirteenth century made it the faith of Burma and Thailand, and by the fifteenth and sixteenth centuries it was the state religion of Cambodia and Laos.

The Burmese and Thai kings styled themselves Dhamma kings. Ordination lapsed in Sri Lanka, and in 1753 the Thai monk Upali went to Kandy to ordain a new line of monks, founding the Siam Nikāya.