While the majority of the Khmer live in Cambodia, approximately 1 million Northern Khmer live across the border in Southeast Thailand. They are primarily concentrated in the provinces of Surin, Sisaket, Buriram, and Nakhon Ratchasima. Their native language, also called Northern Khmer (or Buriram), is distinct from, but similar to, Central Khmer. Since Thai is the only language taught in schools, many Northern Khmer are bilingual, speaking Northern Khmer while at home.
The great Khmer Empire, which flourished between the ninth and thirteenth centuries, encompassed present-day Thailand, Cambodia, Laos, and southern Vietnam. Its power declined when the Thai and Vietnamese conquered the Khmer and restricted them to the area that now known as Cambodia.