Thailand is overwhelmingly Theravada Buddhist, with Pew Research placing the figure near 93 percent, making it one of the most religiously homogeneous large populations in the world; a Muslim minority of about 5 percent is concentrated in the southern provinces bordering Malaysia, particularly Pattani, Yala and Narathiwat, where Malay-speaking Muslims form a local majority.
Buddhism's arrival predates the Thai kingdoms themselves, reaching the region through Mon and Khmer intermediaries by the early centuries CE, and became closely bound to Thai kingship from the Sukhothai period in the thirteenth century onward; the monarch is constitutionally required to be Buddhist and serves as the religion's foremost patron. The Thai sangha, the community of ordained monks, is organized under the Sangha Supreme Council and a 1902 and later 1962 Sangha Act that brought monastic administration under state supervision, while temporary ordination as a monk, often for a matter of weeks, remains a common rite of passage for young Thai Buddhist men. Animist spirit worship, particularly of guardian spirits housed in spirit houses found outside most Thai buildings, coexists with Buddhist practice much as in neighboring Laos and Cambodia, alongside smaller Christian, Sikh and Hindu communities among immigrant populations.