Former prime minister Thaksin Shinawatra can legally file a parole application at the earliest in February next year, according to the Department of Corrections.

Sitthi Sutivong, deputy director-general of the department, said on Monday that an ill convict who is 70 years old or over can apply for parole only after he serves at least one-third of his jail term or at least six months in jail.

As regulations requires the longer period to prevail, Thaksin, 74, must serve at least six months in prison before filing a parole request, Mr Sitthi said. One-third of a one-year jail term is four months.

The six-month waiting period will end in February next year. The administration of his prison can then send a parole request to the Department of Corrections, he said.

Mr Sitthi also said that Thaksin remained at Police General Hospital to receive continuous treatment and the hospital would send a report on the former prime minister's health to the Department of Corrections when his stay at the hospital reaches 30 days (this Thursday).

The department would then decide if he should be returned to Bangkok Remand Prison, Mr Sitthi said.

If Thaksin's condition does not improve or his doctor maintains that he needs continuous treatment at the hospital, the corrections director-general can permit his continued treatment outside the prison, Mr Sitthi said.

Thaksin, 74, returned to Thailand on the morning of Aug 22 after 15 years in self-exile.

The same day the Supreme Court ordered he be imprisoned for eight years for the three cases. His jail term was reduced to one year by His Majesty the King.