BANGKOK: Thailand's former premier Thaksin Shinawatra has submitted a request for a royal pardon, outgoing Justice Minister Wissanu Krea-ngam said on Thursday, his latest move in a long-running power struggle with the country's establishment.

Thaksin, Thailand's most famous politician, made a dramatic homecoming last week after 15 years abroad where he lived in self-exile to avoid prison.

Thaksin arrived on a private jet and greeted supporters before being moved to a prison to serve an eight-year sentence for abuse of power and conflicts of interest from his time in power.

Hours later, Srettha Thavisin of the Shinawatra-backed Pheu Thai party won a parliamentary vote to become prime minister with the support of pro-military lawmakers.

Thaksin, a former telecoms tycoon still wields influence in Thai politics with parties loyal to him winning every election in the past two decades until this year.

This month's events have fuelled speculation that Thaksin has struck a deal with his bitter rivals in the conservative establishment and royalist military, which ousted his parties in coups in 2006 and 2014, at the time accusing him and his parties of corruption and disloyalty to the powerful monarchy.

Thaksin denied those allegations and has rejected talk of a deal with the generals.

On his first night in jail, Thaksin was transferred to a police hospital, on account of chest pains and high blood pressure.

A representative of the 74-year-old Thaksin declined to comment when asked by Reuters about his pardon request.

A request for royal pardon must be submitted through the corrections department to the justice minister.

"The request will then be presented to (incumbent) Prime Minister Prayuth Cha-ocha who needs to sign it before presenting it to the king," Wissanu told Reuters.

If a royal pardon is not granted, Thaksin will have to wait two years to submit another request.