Spelling variants and varieties include the following (Sidwell 2005:11).
Souei. The term "Souei" is also applied to other groups, such as a Pearic community in Cambodia.
Kouy. A textbook in French is published for this variant (Parlons Kouy).
Van der haak & Woykos (1987-1988) identified two major Kui varieties in Surin and Sisaket provinces of eastern Thailand, Kuuy and Kuay. Van der haak & Woykos also identified the following divergent Kui varieties in Sisaket Province, Thailand.
A variety of Kui/Kuy called Nyeu () is spoken in the villages of Ban Phon Kho, Ban Khamin, Ban Nonkat, Ban Phon Palat, and Ban Prasat Nyeu in Sisaket Province, Thailand. The Nyeu of Ban Phon Kho claim that their ancestors had migrated from Muang Khong, Amphoe Rasisalai, Sisaket Province.
The following list of Kuy village locations in Sisaket Province is from Van der haak & Woykos (1987-1988:129). Asterisks (placed before village names) denote ethnically mixed villages, in which ethnic Kuy reside with ethnic Lao or Khmer.