Thailand is a large country in Southeast Asia where approximately 94% of the population call themselves Buddhist.
Animism and Brahmanism were the main religions until Theravāda Buddhism became the official religion during the reign of King Rama Khamheng (1275-1317).
This happened in the 13th century, due in part to missionary monks from Sri Lanka.
As it is actually practised by the majority of the people, Thai Buddhism is more like animism and Brahmanical magic and divination than the teachings of the Buddha.
Efforts by reformers like Ajahn Buddhadāsa to return to more authentic Buddhism have met with little success beyond the educated class.
Thailand’s king is one of only two Buddhist monarchs left in the world.
Sangha, State and Society - Thai Buddhism in History, Ishii Yoneo, 1986.