Northern Khmer people, also known in Thai as Thai-Khmer people (Thai: ไทยเชื้อสายเขมร lit. "Thais of Khmer descent"), is the designation used to refer to ethnic Khmers native to the Isan region of Northeast Thailand.
Khmers have had a presence in this area since at least the time of the Khmer Empire. With the fall of the Angkor, the Khmers of the Isan region were subject to increasing Thai influence. In the 18th century, Thailand officially annexed the former Cambodian province of Surin. The Khmer residents became de facto subjects of the Thai monarchy and a long process of cultural assimilation began.
Although now a minority, the Northern Khmer have maintained some of their Khmer identity, practicing the Khmer form of Theravada Buddhism and speaking a dialect of the Khmer language known as Khmer Surin in Khmer or Northern Khmer in English. Few Northern Khmers are able to read or write their native language due to Thaification policies either enacted or encouraged by the Thai government.
Thai language instruction in public schools has resulted in many of the younger generation being more comfortable using Thai as a medium of communication. Recent renewed interest in Khmer language and culture has resulted in a two-fold increase in the usage of Northern Khmer since 1958.