1964 Joined the Indian Administrative Service in 1964. Postings held in the Indian State of Assam during 64-75, Was S.D.O., North-Lakhimpur (1966–68), Joint Secretary appointment (1968–70), Deputy Commissioner, Darrang, Tezpur (1971–72) and Deputy Commissioner, Kamrup, Guwahati (1973–75). Became life Member of the Indian Institute of Public Administration (IIPA) New Delhi;
1975-79 Deputy Secretary/Director, Ministry of Defence, Government of India, New Delhi;
1980-82 Secretary for all Departments under the Chief Secretary and also Home Secretary, Government of Assam;
1982-84 Jawaharlal Nehru Fellow. Was also member, Assam Planning Board during this period;
1984-89 Joint Secretary to the Government of India, Ministry of Steel and Mines, New Delhi. Was also Chairman and Managing Director, Hindustan Copper Limited for one year;
1989-90 Queen Elizabeth Fellow, Oxford University, U.K;
1990-92 Agricultural Production Commissioner and Special Commissioner and Special Secretary, Government of Assam, Agriculture. Panchayat and Rural Development, Fisheries and Animal Husbandry Department, Dispur, Guwahati. Was awarded Governor of Assam Gold Medal in 1991 for outstanding service in Assam;
1992-93 Joint Secretary and later Additional Secretary to the Government of India, Ministry of Home Affairs, New Delhi. Devised regional planning and Development models in tribal areas;
1993-95 Additional Secretary, Ministry of Environment and Forests, Government of India, New Delhi, Chairman of the National Committee on Bio-diversity Conservation. Asia Representative on Ramar Convention on Wetlands, Gland, Switzerland. Director, Indian School of Forest Management, Bhopal for one year. Life Member of the Society for Promotion of Wasteland Development (SPWD), New Delhi;
1995-97 Union Culture Secretary. Became Life Member of the Indian National Trust for Arts and Cultural Heritage (INTACH) organized global level Golden Jubilee celebrations of India’s Independence. Set up National Culture Fund;
1997-99 Union Home Secretary, Secretary, Justice, Government of India and Secretary, Jammu and Kashmir Affairs, Government of India. Recipient of Gulzarilal Nanda Award for the year 1998 for outstanding public service in India from the President of India;
1999-02 Executive Director, The World Bank and its Affiliates representing India, Bangladesh, Bhutan and Sri Lanka. Founder Member of the Board of Governors of Development Gateway Foundation (DGF) and member, Global Environment Facility (GEF), Washington D.C.;
2003-07 A variety of honorary academic and governmental assignments including (i) Chancellor of the Central University of Tibetan Studies, Sarnath (ii) Chief Editor of the South Asia Series on "Perspectives on Economics, Technology and Governnance" Oxford University Press,New York. (iii) Chairman, National Commission for Economically Backward Classes set up by Govt. of India: and (iv) Mahatma Gandhi National Fellow; Was honoured the first Man of Letters Award by the Dalai Lama on 11 June 2003 at New Delhi;
2008-13 Governor of Sikkim; Also President, Namgyal Institute of Tibetology, Gangtok and Chancellor, Sikkim Manipal University;
2014 onwards B.P.Singh worked on a book “The 21st Century:Geo-politics, Democracy and Peace” being published by Routledge (New York & London, during 2017). Also working for promotion of science, culture and world peace.
Public speaker: have been accepting speaking assignments on subjects such as Peace, Democracy, Culture, Security, Ecology and Governance, within India and abroad.