A Thai elephant gifted to Sri Lanka two decades ago arrived back in its birth country on Sunday, following a diplomatic spat over the animal's alleged mistreatment.

Thai authorities had gifted the 29-year-old Muthu Raja – also known back in its birthplace as Sak Surin – to Sri Lanka in 2001.

But they demanded the elephant back last year after allegations that it was tortured and neglected while kept at a Buddhist temple.

The 4,000-kilogrammemammal arrived in Thailand in the afternoon, having been transported inside a specially-constructed giant steel crate onboard an Ilyushin Il-76 cargo plane.

"He arrived in Chiang Mai perfectly," said Thai environment minister Varawut Silpa-archa, speaking from the airport. "He travelled five hours and nothing is wrong, his condition is normal."

"If everything goes well, we will move him," he added, referring to plans to quarantine the elephant at a nearby nature reserve.

The elephant was moved from its temporary home at a zoo in Sri Lanka's capital Colombo before dawn, accompanied by four Thai handlers and a Sri Lankan keeper, with two CCTV cameras monitoring its health in transit.

It left Colombo in the morning on a commercial reparation flight that Thai officials said cost US$700,000.

Muthu Raja was in pain and covered in abscesses when it was rescued from the Buddhist temple last year, the zoo's chief veterinarian, Madusha Perera, said. Animal welfare groups said the elephant had been forced to work with a logging crew and that its wounds – some allegedly inflicted by its handler – had been neglected.

The elephant will undergo hydrotherapy in Thailand to treat a remaining injury on its front left leg, Perera said. (AFP)