He was the non-resident ambassador to the Vatican and Spain, as well as Singapore's representative to the ASEAN Intergovernmental Commission on Human Rights.
Desker also serves as the chairman of the board of governors of Singapore Technologies Marine.
Desker served as Singapore's Deputy Permanent Representative to the United Nations in New York from 1982 to 1984.
He retired from the foreign service in 1993 and was appointed the chief executive officer (CEO) of the Trade Development Board (1994-2000).
Desker took over as director of the Institute of Defence and Strategic Studies (IDSS) in 2000.