Comparisons of Phu Thai with other Tai languages such as Tay Khang[citation needed] have not yet been done systematically enough to yield convincing results.

Whether in the Phu Thai areas of Central Laos or in more recent locations of Northeastern Thailand, one can find, along with Phu Thai, a few Katuic dialects known locally as Bru, So or Katang.

James R. Chamberlain (2012) focusing on anthropological issues describes “the Phou Thay – Brou relationship” as a “symbiosis” and states that “the Phou Thay – Brou relationship has never evolved into a feudal system”.

Phu Thai speakers live as well in the Khammouane and Savannakhet Province of Laos.

There is little dialect differentiation between the varieties spoken in central Laos and in northeastern Thailand.