He was also a politician, serving as a member of the Lok Sabha for twenty-five years, from 1952 to 1977, and an international clay pigeon and skeet champion.

He saw active service in the Second World War, serving in the Middle East with his grandfather, General Sir Ganga Singh, the 23rd Maharaja of Bikaner.

In 1952, the young Maharaja Karni Singh was elected Member of Parliament in the Lok Sabha (Lower House) of India from Bikaner constituency as an independent candidate, serving on several consultative committees of different ministries and holding his seat until 1977.

In 1964, he received the degree of Doctor of Philosophy from Bombay University, for his thesis The relationship of the Bikaner royal family with central authority (1465–1949).

Singh won the National Championship in Clay Pigeon Trap and Skeet seventeen times and represented India at all levels of international competition.

Singh was also a keen player of tennis, golf, and cricket, and held a private pilot's licence.