Lạng Sơn Province
Ba Thín () is a tributary of the Kỳ Cùng River. It originates in the high mountains of Guangxi, China, and joins the Kỳ Cùng River in Qu Xa commune in Lộc Bình District of Lạng Sơn Province in northeastern Vietnam. The river is long and has a catchment area of .