 Born on 27 July 1945 at Chare, a small village in Tuensang district of the Northeast Indian state of Nagaland to Hopongki, Sangtam did his early schooling at St. Edmund's School, Shillong (1962) and completed his pre-university course at St. Edmund's College, Shillong in 1964.He started his graduate degree from St. Stephen's College, Delhi and completed it in 1970 from the Fazl Ali College, Mokokchung in Nagaland.Aligned with the Indian National Congress, he is a member of the Nagaland Pradesh Congress Committee, serving it as a joint secretary in 1987 and as a secretary in 1989.