This work is about the relationships between the Karen and Khon Muang (local Thais) on the Moei River bank in Tha Song Yang district, Tak province and those on the other bank in the Karen State of Myanmar. The study divided the relationships into three periods. The first period was before the formation of modern states until 1967, when Britain, Thailand and Myanmar did not come to manage the Karen area and local people were free to claim land ownership. The second period was the formation of a buffer state from 1967 to 1987, when the Karen State and Thailand controlled the area with the trade of timber and consumer goods between Thai and Karen residents. This period was a modern development, the formation of the Karen Liberation Army on the Burmese side, and awareness of being Thai through the Thai formal education system. The third period was the collapse of the buffer state, forcing the Karen soldiers to take refuge on the Thai side. On the Burmese side, soldiers of different armies took control of the area. On the Thai side, strict enforcement on cross-border migrants and consumer goods was conducted, bringing about a discourse on transnational labor and refugees that became detrimental to national security.