The known early history of Thailand begins with the earliest major archaeological site at Ban Chiang.
Dating of artifacts from this site is controversial, but there is a consensus that at least by 3600 BCE, inhabitants had developed bronze tools and had begun to cultivate wet rice, providing the impetus for social and political organisation.
Migrations from southern China to Southeast Asia took place primarily during the first millennium CE, most likely via northern Laos.
Between the 6th and 9th centuries CE, Buddhism was introduced into the Tai-speaking lands, probably via Burma, and became the dominant religion.
The Theravada Buddhism now practised in Thailand was introduced by missionaries from Sri Lanka in the 13th century.