The article analyzes the process of forming and establishing the border between Vietnam and Cambodia in southern from the time the Vietnamese arrived in Mo Xoai and Dong Nai areas to reclaim land and establish villages (17th century). When the Vietnamese people's resistance war against the French ended successfully (July 1954). In the 17th - 18th centuries, along with the step of“South progress”, the Vietnamese gradually explored and established villages in the Dong Nai River area, then moved down to the vast lower Mekong River, creating a premise for the Nguyen lord's government gradually merged the lands here into the territory of the Dang Trong land. The borderline between Cochinchina - Chan Lap in this period was initially established, but it was still unclear and fluctuated frequently. In the early nineteenth century, the early kings of the Nguyen Dynasty (Gia Long, Minh Mang, Thieu Tri, Tu Duc) had a certain interest in the western border area of Cochinchina. The border between Cochinchina and Cambodia was basically established on the basis of consensus between the Dai Nam court and the Cambodian court. During the French colonial period, the French government paid special attention to the planning of the border between the colonial Cochinchine region (Cochinchine Française) and Cambodia, by means of treaties between the two governments, drawing authentic maps and marking landmarks on the field.

borderline in South Vietnam, Vietnam, Cambodia, Cochinchina, 17th century, the early 20th century