BANGKOK — Jailed former Thai prime minister Thaksin Shinawatra has undergone orthopaedic surgery, prison officials said — his second operation in the space of a few weeks.

The 74-year-old billionaire, ousted as PM in a 2006 coup, returned to Thailand from 15 years of self-exile in August and was immediately jailed on old graft and abuse-of-power charges.

Thaksin was transferred to a police hospital just hours after being jailed, because of his poor health, and last month his daughter said he had had an operation, without giving details.

The Department of Corrections said in a statement late on Monday (Oct 23) that earlier in the day Thaksin had undergone five hours of orthopaedic surgery.

He was recovering in an intensive care unit, the statement added, without giving further details.

"The director general of the Department of Corrections has ordered the Bangkok Remand Prison chief to supervise the operation," the statement added.

The former premier's homecoming coincided with his Pheu Thai party's return to power — thanks to a controversial deal with pro-military parties — prompting rumours of a backroom deal.

Days later, King Maha Vajiralongkorn cut Thaksin's sentence from eight years to one year. 

Local media reported Thaksin had been suffering from chest tightness and high blood pressure, and 10 days ago published a photo of him being transferred to a bed from the police hospital for CT and MRI scans. AFP