Jailed former Thai prime minister Thaksin Shinawatra is to be freed, the government said Tuesday, possibly as soon as the weekend -- just six months after returning from 15 years of self-imposed exile.

The controversial billionaire, twice elected premier and ousted in a 2006 military coup, was jailed upon his return to Thailand in August for eight years on graft and abuse-of-power charges, but within days had his sentence cut to one year by King Maha Vajiralongkorn.

Justice Minister Tawee Sodsong said Tuesday that Thaksin, 74, would be among 930 prisoners granted early release.

"He is in the group where they are in a critical condition or aged over 70. He will be released after six months automatically," Tawee Sodsong told reporters.

Thai media reported that the former Manchester City owner's release could come any day from Saturday.

His homecoming coincided with his Pheu Thai party returning to government in alliance with pro-military parties, leading many to conclude that an agreement had been struck to cut his jail time.

The rumours grew stronger when he was transferred to a police hospital within hours of being sentenced because of his poor health, and it is not clear that he has spent any time in a prison cell.

Local media reported Thaksin had been suffering from chest tightness and high blood pressure when he was admitted to hospital, and his family said he had undergone two operations in the following months.

Prime Minister Srettha Thavisin, of the Pheu Thai party, confirmed Thaaksin would be freed and insisted the move was in line with the law, saying "he already served his jail time".

"Thaksin was our prime minister for many years," Srettha told reporters, saying Thaksin was still "adored" by many people.

"I am sure that he can give us some great tips. I would like to reiterate that everything was done according to the law of the Department of Corrections."

The exact details of Thaksin's release are not clear, but he may be subject to monitoring -- possibly with an ankle tag -- and restrictions on his right to travel.

His daughter Paetongtarn Shinawatra, the current head of Pheu Thai, welcomed the news.

"He already served his jail term for six months in a limited space," she said.

"I think it's time for him to live the rest of his life happily."

- Divisive figure -

Former telecoms tycoon Thaksin is one of the most influential but divisive figures in modern Thai history.

Loved by millions of rural Thais for his populist policies in the early 2000s, Thaksin is reviled by the country's royalist and pro-military establishment.

Much of Thai politics over the past two decades has been coloured by the tussle for power between the establishment and Thaksin and his allies.

When he landed home in Bangkok, his supporters gave him a hero's welcome, and his first public act was to prostrate himself in homage before a portrait of the king at the airport.

Police laid lese-majeste charges against him last week over comments he made in South Korea almost a decade ago, though it is not clear whether prosecutors will take the case to court.

Thaksin denies the charge and has written to the attorney general asking for fair treatment.