This paper analyzes the cooperation relationship between Thanh Hoa (Vietnam) and Huaphanh (Lao PDR) Provinces on the aspects of cross-border cooperation through issues on planting border markers, coordination in the handling of invasion, cross-border management, border protection, and bilateral boundary system. Based on this, the paper confirms achievements, limits, and lessons with regard to boundary affairs between Thanh Hoa and Huaphanh Provinces from 1977 to the present.