The diversity of Southeast Asia can be also represented at the tremendous number of ethnic groups residing throughout its various regions even beyond national boundaries. What does it mean by the composite of numerous peoples? It has triggered a lot of problems in a nation or overall Southeast Asia. Among them, the most serious one seems to be ethnic conflicts having damaged national integration and caused political, economical, and social instability. In that respect, Karen people have been a minority group situated in the most chronic dispute in Myanmar. Since 1947 some of the Karen equipped with armed forces have been fighting against the military government currently ruling Myanmar. As the result, the refugees over 200,000 population had moved to the mountain camps located at neighboring Thailand, attracting a lot of attention throughout international societies. According to 1931 census by British colonial government, the Karen have the greatest numbers in population as minority and include 16 subgroups including Karenni(Kayah) and Pa-O seemingly excluded from its category in contemporary point of view. It means that Karen people should not be regarded as an ethnic group, and in fact do not show a homogeneous identity under the title of Karen. Given the situation, we need to reconsider the category of Karen. What does the Karen mean in a real sense? Previous studies on the Karen had been performed mainly by anthropologists or missionaries such as Marshall(1922), Hamilton (1976), Hanson Tadaw(1959), Smeaton(1920), Keyes(1979), Hayami (1992; 2004), etc. Most of them examined the Karen as a group and ignored the possibilities of representing the divergent identities vis-à-vis their subgroups. Therefore, they have focused on the myth to convert Karen people to Christianity, although the Christian Karens are less than 20% of total population. As a result, I argue that they would fail to define the real meaning of Karen. It has been caused us to recognize the Karen as a meaningless total entity to be accepted by all means. According to their arguments, the difference among Karen's subgroups is just dealt with the trivial matters that do not affect the ethnic boundary itself, still maintaining the ethnic identity as Karen. As we shall see on this thesis, this is never the case. My thesis aims at uncovering and scrutinizing the real meaning of the category of Karen. For the purpose of it, I will consider Karen people as a linguistic group from the beginning as shown in 1931 census. I argue that the Karen have been affected or exposed by various conditions or environments throughout the harsh history having happened on the areas of current Myanmar and Thailand, leading the vicissitudes of their ethnic identities.