"..This paper presents the results of a sociolinguistic survey of the Pwo Karen people in northern Thailand, with a special focus on those located furthest from the center of literature development in Chiang Mai province. It was hypothesized that the Pwo Karen in some areas of northern Thailand speak a language unintelligible with the Northern Pwo Karen language of Chiang Mai province. Therefore, the purpose of this survey was to determine whether there are any unintelligible varieties and whether there is any further need for language development among the Pwo Karen of northern Thailand. Language vitality, attitudes, and bilingualism were assessed using sociolinguistic interviews. Intelligibility was assessed using recorded text testing, and lexical similarity was assessed using wordlists. The survey’s conclusion is that further language development would be beneficial, because Pwo Karen is a vital language in northern Thailand, and there is substantial variation among speech varieties. Language development, however, might not include development of written materials in every dialect or group..."