 He joined the Indian Civil Service and served as Regional Commissioner for the Eastern States, a member of the Constituent Assembly of India, joint secretary for India's Defense Ministry, Director-General of Transport, and special secretary in the Ministry of Information and Broadcasting.Between 1966 and 1972 Singh was secretary to the President of India, then from 1 October 1972 to 6 February 1973 he was Chief Election Commissioner of India.In 1966, 1969, and 1975, he was appointed as a representative of India in the United Nations Assembly and served on the United Nations International Law Commission on a part-time basis from 1967 to 1972.