It can be confusing. In addition to the names that each tribe has for themselves, and the names of the tribes in English and Thai, each tribe also has its own name for every other tribe (these terms are called autonyms and exonyms, respectively). It can be very, very confusing. Below we have assembled a matrix of what each of the seven main ethnic groups of the area call each of the seven ethnic groups. If you are counting, that’s 49 different names. Phew!
In this website we try to use a romanization of the name that the tribe calls itself. The exception for that is the Karen, because it already has a standardized English name, and the name which is uses to refer to itself is very difficult to spell in English.
We have also included the traditional opinions or stereotypes that each tribe has towards the others and themselves. We haven’t listed these to assign any sort of value judgment or superiority/inferiority among the different ethnic groups, but, instead, to show how complicated the relationships between the various ethnic groups in Northern Thailand are.
So the Karen call the Lisu Kae Lisaw and the Lisu call the Karen Ya-geu-leu; furthermore, “Lisus have always gotten along with Karens because they have never tried to take advantage of each other.” I can’t tell you how much I love this stuff, and I wish somebody would replicate the matrix for other areas of the world. (Nigeria would be an excellent start.)
I found it at MetaFilter, by the way.