This investigation focused on the ethnic interaction between two groups of the Karen, whose settlements were at Bongti border area in Sai Yok district, Kanchanaburi province. They included the inside Karen, who had long been in the Thai border and the outside Karen, who migrated into Thailand after the demarcation between the two countries was established to create national unity. The demarcation had affected the long relationship between the two groups. The latter group was thus deprived of Thai citizenshipas well as political and economic benefits. Due to their close kinship and relationship, the former group exploited this gap by facilitating the latter group to migrate into Thailand and to help them adjust after they were pushed to become stateless. This attempt enabled the latter group to maintain their ethnicity in place of the former group who had become naturalized Thais.