Born in 1923 at Kewzing, a south Sikkimese village at the foot of Kangchenjunga in Northeast India, Sonam Gyatso started his career in 1946 as a school teacher at Lachung, in the northern part of the state. After three years of service, he joined the Frontier Constabulary Force of the Indian Air Force as a head constable in 1949 which gave him the opportunity to attend a basic mountaineering course at the Himalayan Mountaineering Institute, Darjeeling in 1954. His first chance at mountaineering came in 1957 when he was selected for the Nanda Devi expedition, but the attempt was unsuccessful. However, he completed his first successful expedition when he scaled the 26,897 ft of Cho Oyu peak in 1958, as a member of an all-Indian expedition, the first time an Indian team climbed a peak of that height.