Southeast Asia is a land of multi-ethnic groups. Living together in the same land has brought about good and bad relations. The Karen ethnic group is very important in the region, and their history cannot be clearly defined because there are no written records, only oral. The group always believe that they have been taken advantage of by bigger ethnic groups, particularly the Tai. The Tai is the largest ethnic group in mainland Southeast Asia. The historical relations between the two groups are both friendly and competitive. Whatever they are, the Karen are always losers and eventually become assimilated. Karen anecdotes appear in Burmese, Shan, Mon and Thai historical evidence. The evidence always indicates that the ethnic group was dominated, being frontier rangers and soldiers of the Thai state as well as providing political tributes to Thai rulers. These duties might have been a deciding factor for the ethnic group to have a role in Thai society. They have been an important source of forest products and in the establishment of significant frontier towns. Their importance has also easily led to them becoming Thai citizens. At the same time, their strategic importance was required by the Burmese and the British. Thus, the Karen have been surrounded by groups wanting to dominate them. Karens being Thai citizens in the Central region have been treated differently from Karens in the Lanna region. Lanna people want to dominate and exploit the ethnic group while central Thai people want them to help the country. State policies have had strong impacts on the Karen. In the reign of King Rama V, the group was so important to the country that they were almost granted Thai citizenship. However, ethnic policy changes during the reign of King Rama VI reduced the significance of their role, suppressed their ethnicity, and finally assimilated them. Although they are now Thai citizens, they still feel abandoned and do not have full rights, whether it is in the past or the present.