Mr Tan Chong Kin, who was chairman of the People's Action Party (PAP) for 10 days in 1957 when the communists took over the party, was to be released from political detention after denouncing communism.
In a government release in late December 1965, Mr Tan, also known as Chan Chong Kin, was quoted as saying: "I have decided to reject communism totally.
"Now that Singapore is an independent and sovereign state, colonial rule is ended and, therefore, there is no need for further colonial struggle," he added.
Mr Tan was arrested in October 1963, when he was a ranking member of the Singapore Association of Trade Unions and the secretary of the Singapore Motor Workshop Employees' Union.
Both had been used for communist activities.
The English-educated Mr Tan had joined the Communist Party in 1950.
He got into the Farrer Park branch of the PAP in 1955.
By the end of 1956, he had secured a place in the party's central executive committee.
When the communists captured the PAP in August 1957, Mr Tan became the party chairman, but only for 10 days as he was then arrested by the Special Branch, together with other leftists in the PAP, in an anti-communist operation.
He and other detainees were released in 1959.
He joined the Barisan Sosialis and unsuccessfully contested the Anson ward in the 1963 election.
He had worked actively for the communist cause until his arrest, said the government statement.