Thailand's divisive ex-leader Thaksin Shinawatra was jailed on Tuesday as he returned to the kingdom after 15 years in exile, hours before parliament votes to install his party's candidate as the new prime minister.

The billionaire landed in a private jet at Bangkok's Don Mueang airport in the morning, to be greeted by hundreds of noisy "Red Shirt" supporters waving banners and singing songs.

Thaksin emerged briefly from the terminal building to bow and offer a floral garland at a portrait of King Maha Vajiralongkorn as a mark of respect before waving to supporters.

More Red Shirts lined the streets as the former Manchester City owner was taken to the Supreme Court.

There, he was ordered to serve eight years for three convictions passed in his absence – one linked to his former Shin Corp company, another linked to a bank loan, and a lottery case.

His return came on the day parliament is expected to install business tycoon Srettha Thavisin as prime minister at the head of a coalition led by the Pheu Thai party – the latest incarnation of Thaksin's political movement.

Thaksin, 74, was convicted in four cases in his absence, although the statute of limitations has expired in one.

Even after the court ruling, it is unclear how long Thaksin will stay in jail.

The timing of his return, as his party assumes power, has led many to speculate that a backroom deal has been done to allow him leniency.

"Welcome back to Thailand daddy. My father has now arrived in Thailand safely and has entered the legal process," his daughter Paetongtarn wrote on Instagram, with a photo of Thaksin with his three children and seven grandchildren in the airport's VIP lounge. (AFP)