Songtsän Gampo
Sherdukpen society is divided into two classes: The Thong and Chao, the former of which–the higher caste–are divided into eight clans. Marriage between castes are considered taboo within the tribal society and are strongly discouraged. Local legend mentioned that the upper caste are the descendants of a Tibetan king (a grandson of Songtsän Gampo) and Ahom princess, of which they bore two sons. The Chao are the descendants of the king's porters and servants. The Sherdukpens migrate to Doimara (a lowland hamlet close to the Assamese border) and stayed between December to March on an annual basis during the winter months, a tradition with which the tribe maintain the memory of their Assamese ancestry. In Doimara, the Sherdukpens mingled with the nearby Assamese natives and traded for rice.