BANGKOK, Sept 9 (Reuters): Thailand's influential former prime minister Thaksin Shinawatra was sent to prison on Tuesday after the Supreme Court ruled his time in hospital detention was an attempt to avoid jail, a major blow for a powerful family that has dominated politics for two decades.

The polarising billionaire had spent only a few hours in prison upon his return from 15 years of self-exile in August 2023 before he was hospitalised after complaining of heart trouble and chest pains, prompting widespread scepticism and public outrage.

His eight-year sentence for conflicts of interest and abuse of power while premier from 2001-2006 was commuted to one year by the king and Thaksin was released on parole after just six months of detention, the entirety of which he had spent in the VIP wing of a hospital.

The judges on Tuesday said Thaksin had no severe illness and could have been treated in jail, adding both he and his doctors had intentionally prolonged his hospital stay.

"The defendant knew the facts or was aware the situation was not a critical emergency. The defendant only had a chronic condition that could be treated as an outpatient and did not require hospitalisation," it said.

A corrections department vehicle carrying Thaksin was seen arriving at a Bangkok jail less than an hour after a ruling that has gripped the country, the latest drama in two weeks of political chaos that saw the fall of another Thaksin-backed populist government.

The 76-year-old power-broker is experiencing a period of political reckoning after his daughter and protégé Paetongtarn Shinawatra was sacked as prime minister by a court on August 29 - the sixth premier from or backed by the Shinawatra family to be removed by the judiciary or military.

Paetongtarn's government fell on Friday, outmanoeuvred by challenger Anutin Charnvirakul, who was elected premier by parliament in a humiliating defeat for Thaksin's once unstoppable Pheu Thai party, which won five of the past six elections.

Thaksin, who has loomed large over Thai politics throughout a quarter of a century of turmoil, is Thailand's first former premier to be sent to prison.

Photo from Reuters