Kelantan–Pattani Malay (Malay: bahasa Melayu Kelantan–Patani; Thai: ภาษายาวี; baso/kece Patani in Pattani; baso/kecek Klate in Kelantan) is an Austronesian language of the Malayic subfamily spoken in the Malaysian state of Kelantan, as well as in Besut and Setiu districts of Terengganu state and the Perhentian Islands, and in the southernmost provinces of Thailand. It is the primary spoken language of Thai Malays and used as a lingua franca by ethnic Southern Thais in rural areas, Muslim and non-Muslim and the Sam-Sam, a mostly Thai-speaking population of mixed Malay and Thai ancestry.
Kelantan–Pattani Malay is highly divergent from other Malay varieties because of its geographical isolation from the rest of the Malay world by high mountains, deep rainforests and the Gulf of Thailand. It is also influenced by Thai in Thailand.