Former Thai leader Thaksin Shinawatra returned from 15 years in exile on Tuesday and was immediately jailed, but his time behind bars could be cut short with his party on the edge of winning back power.

The divisive billionaire landed in a private jet at Bangkok's Don Mueang airport at 9 am (0200 GMT), to be greeted by hundreds of noisy "Red Shirt" supporters waving banners and singing songs.

Thaksin, 74, 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.

But it was unclear how long Thaksin would stay in jail.

His return came just hours before parliament was expected to install business tycoon Srettha Thavisin as prime minister at the head of a coalition led by the Pheu Thai party/ which is the latest incarnation of Thaksin's political movement.

The timing of Thaksin's return, with his party on the verge of assuming power, has led many to speculate that a backroom deal has been done to allow him leniency.