Former prime minister Thaksin Shinawatra has the same rights as all other inmates to receive further reductions to his jail sentence, said former deputy prime minister Wissanu Krea-ngam.

Thaksin is staying at the Police General Hospital's premium ward while serving his jail term after returning to Thailand from 15 years of self-imposed exile.

Mr Wissanu was responding to reports quoting him as saying the royal pardon already granted to Thaksin, which resulted in his combined 8-year jail term being commuted to one year, was final and he had no right to apply for more leniency.

Mr Wissanu said he was misquoted and what he actually meant to say was that the royal pardon made public on Friday was a royal decision that was final.

He said he didn't say a word about Thaksin losing his other rights to further jail sentence reductions or a new pardon.

Whatever rights other prisoners with one year or less to serve may have, Thaksin has those rights too, said Mr Wissanu.

"[Thaksin's remaining jail term] could still be further reduced. But whether it will be reduced or not, I don't know. Some expect it to be cut further on the occasion of Father's Day (Dec 5)," he said.

The pardon was granted on Friday.

Upon his return, Thaksin was sent to Bangkok Remand Prison after the Supreme Court sentenced him to eight years in prison for three cases.

Within 13 hours, he was transferred to the Police General Hospital, suffering from chest pain, hypertension, and low blood oxygen saturation. He has remained there since.