Four years ago he was allowed to leave and live on the mainland with his elderly parents. Now, some 30 years after being arrested under the British- devised Internal Security Act, the restrictions on Mr Chia's movements keep flowing.
At the end of last month he was issued with a new restrictions order, lifting some restrictions but retaining all curbs on participation in political or community activities.
A painfully thin, soft spoken 55-year-old with bad eyesight, Chia Thye Poh does not give the impression of being a serious threat to national security. Asked whether it is true that he is one of the longest-serving political prisoners, he says, "I was only in jail for 23 years". There is not a hint of irony in the use of the word "only".
Although tiny, Singapore seems to breed some very tough characters. The politics of the island state have been dominated by the tough and unflinching Lee Kwan Yew, who devised a system of iron rule with little space for opposition.
Yet the opposition has not been snuffed out because there are some equally tough people on the other side of the fence. None more so than Mr Chia.
He could, at the stroke of a pen, end his restrictions, indeed he could have secured early release from jail or have accepted an offer to be granted asylum in Canada, but Mr Chia is made of sterner stuff. The government wants him to renounce the banned Communist Party's use of force and terrorism. He insists that as he has never been a party member and never advocated terrorism, he cannot renounce beliefs he has not held. "I wouldn't be able to live in peace. I cannot go against my conscience," he says.
It took the Singaporean government 18 years to give a reason for Mr Chia's detention. When it did, in 1985, it bluntly stated that Mr Chia had been instructed by the Communist Party to infiltrate the Barisan Sosialis Party to ferment illegal demonstrations and strikes to destabilise the government.
Mr Chia gives a different version of events, saying that far from joining the Communist Party, he joined the legal Barisan Sosialis, became a member of parliament and resigned after the ruling People's Action Party decided to pull out of the federation with Malaysia.
His captors used to taunt him by taking him out on car drives to show how the country was developing while he remained incarcerated. Just sign this little piece of paper, they said, and you can be part of these exciting new developments. But Mr Chia remained unmoved.
His situation was, in many ways, a stand-off. He refused to sign the paper and the government said he could therefore expect to rot in jail for ever. They might have realised that he would be a tough nut to crack. Solitary confinement in a darkened room, confinement in an oven-like cell, two hunger strikes and a bout of forced feeding did nothing to shake him.
Mr Chia now inhabits a Kafka-esque world. When living in Sentosa he was forced to live in a one-room former guard house and told he had to pay rent for it. As he had no money he was offered a job as an assistant curator, but discovered that this was a civil service post, meaning he would need to obtain the permission of his boss before speaking to the media.
So he declined and worked as a freelance translator. Now that he is of an age when jobs are hard to come by, he is free to find a job with an employer of his choice. Similarly, now that he has practically no money, he is free to move out of his parents house and live where he likes.
His internal security minders urge him to get out and about more and see the many changes which have occurred in Singapore, but he asks them, "How do you expect a person without freedom to have a mood for sightseeing?"
Instead Mr Chia spends most of his time in the anonymous Ang Mo Kio public housing estate, confident that he will eventually be vindicated.