The Kai-Souk languages are a language family on mainland Southeast Asia, also known as Indochina. These languages are the only extant branch of the Song language family. Souk is the most widely-spoken of the family; the remaining Kai-Souk languages are spoken almost exclusively by isolated hill tribes.
The language family is so named due to most of its speakers being very closely related to the Kai people; in fact, almost 15% of Kai people do not speak Souk as their native language, but instead a dialect which has become mutually unintelligible with Souk. The Kai-Souk languages were all once simple dialects of Old Souk, which eventually evolved into proper languages mutually unintelligible with Souk, which is itself the direct descendant of Old Souk; thus Souk is described as the oldest language of its family.
The Kai-Souk languages are generally transcribed according to the Kai-Souk Colonial Alphabet.