The ruling is another major blow for the powerful Shinawatra family that has dominated politics for two decades.

Thailand's former Prime Minister Thaksin Shinawatra poses with his daughter Paetongtarn Shinawatra as they arrive at the Supreme Court in Bangkok on Sep 9, 2025. (Photo: AFP/Lillian Suwanrumpha)
Thailand's Supreme Court on Tuesday (Sep 9) ruled billionaire Thaksin Shinawatra improperly served a 2023 prison term in a hospital suite, ordering him to serve one year of jail time.
"Sending him to hospital was not legal, the defendant knows his sickness was not an urgent matter, and staying in hospital cannot count as a prison term," said the ruling read out by a judge.
The court also said the detention was not served according to procedure.
Police would take Thaksin into custody, a Reuters reporter who attended the verdict said.
Speaking to reporters outside the court, his daughter Paetongtarn Shinawatra decried the ruling, adding that Thaksin was the first Thai prime minister to go to prison despite the "good he has done for the country".
She also expressed concern for his health given the new circumstances.
Thaksin was elected prime minister in 2001 and again in 2005, but took himself into exile after his second term was cut short by a military coup.
On his return in August 2023, he was sentenced to eight years in prison for corruption and abuse of power.
However, he spent only a few hours in jail before being transferred to a private room in Bangkok's Police General Hospital after complaining of heart trouble and chest pains, prompting widespread scepticism and public outrage.
His sentence for conflicts of interest and abuse of power was commuted to one year by the king and Thaksin was released on parole after just six months, the entirety of which he had spent in the VIP wing of the hospital.

Thaksin's entourage is facing a period of political reckoning after his daughter and protégée Paetongtarn was sacked as prime minister by a court 11 days ago - the sixth premier from or backed by the Shinawatra family to be removed by the judiciary or military.
Days of chaos ensued before 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.
Thaksin landed back home on Monday after leaving Thailand last week, quelling speculation that he had absconded from the inquiry.
In a post on X, Thaksin said he left Thailand for a medical check-up in Singapore, but that his plane was diverted to Dubai because of an airport closure.
Last month, a royal insult case against him was dismissed after a court cited insufficient evidence to prove any wrongdoing.
The case stemmed from a 2015 media interview Thakisin gave during his long stint in self-imposed exile. It was brought by the country's royalist military that ousted both Thaksin and his sister Yingluck Shinawatra from power in coups in 2006 and 2014, respectively.
Thaksin had faced a jail term of up to 15 years.
Additional reporting by Saksith Saiyasombut.