Mr Chia served 23 years in jail without trial. In 1989 he was released but was banished to the island of Sentosa, which had been turned into a Disney-style theme park. Seven years ago he was allowed to leave the island, though restrictions were still maintained on his movements and place of residence.
These have finally been removed though he has been warned that renewed participation in his allegedly subversive activities will meet with a harsh response.
Mr Chia could have extricated himself from jail much earlier by admitting he was a Communist and by renouncing the use of force and terrorism. But in an interview with The Independent, made while he was still under restrictions, he said he could not accede to this because he never had been a Communist and had never advocated terrorism.
"I wouldn't be able to live in peace. I cannot go against my conscience," he said.
The government claimed he was ordered by the Communists to join the legal Barisan Socialist Party and encourage demonstrations and strikes to destabilise the government.
He says his real offence was to be elected to parliament and then resign in protest against the government's decision to pull out of the federation that formerly linked Singapore to neighbouring Malaysia. The government's case has not been heard because Mr Chia has never appeared in court for trial. Indeed, it took the authorities 18 years to give a reason for his detention.
In a television interview yesterday, Mr Chia was not celebrating his release. "The best part of my life was taken away, just like that," he said.
He called for the abolition of the Internal Security Act, which is also in force in Malaysia, where it was used to arrest the former deputy premier Anwar Ibrahim. He believes he scored some kind of pyrrhic victory by surviving his long jail term and restrictions on his freedoms.
The decision finally to restore his freedom is part of a number of moves under way in Singapore to ease the heavy hand of government on this highly controlled society.