The Kui (Kuoy, Soai) are a group of more than 100,000 located in east-central Thailand, northeast Cambodia, and Laos. Some experts suggest that the Kui were settled in the area prior to the arrival of the now-dominant Thai and Lao. The Kui are closely related to the Chaobon, Chong, Pear, and other similar groups. They have been drawn into the dominant cultures in the region: the traditional religion now has largely been replaced by Buddhism, many Kui now speak Khmer or Lao, wet-rice agriculture has replaced horticulture, and there is frequent intermarriage with the Khmer.
Seidenfaden, Erik (1958). The Thai Peoples. Bangkok: Siam Society.