Vets are preparing to airlift an Asian elephant from Sri Lanka back to its home country of Thailand this weekend, after it spent more than two decades at a Buddhist temple where activists alleged it was abused.

The Thai royal family gave the elephant as a gift in 2001 to Sri Lanka’s government, which in turn gave it to the temple where it was named Muthu Raja and given honoured roles in religious processions.

However, the activist group Rally for Animal Rights and Environment, or Rare, alleged it was being mistreated, including that it had a stiff leg from a long-neglected injury.

It lobbied last year for the intervention of Thai officials, who asked Kande Viharaya temple officials to allow the animal’s return to Thailand for medical treatment.

“This is not the end, but the beginning of a new life for Muthu Raja,” Rare group founder Panchali Panapitiya said.

The temple agreed to transfer the elephant last November to Sri Lanka’s National Zoological Garden, where it has been receiving treatment and preparation for the airlift to Thailand on Sunday.

Madusha Perera, a vet at the zoo, said two big abscesses the elephant was suffering from when it arrived have mostly healed. However, the zoo has not been able to fully treat the animal’s leg because of a lack of facilities, she said.

“Once he gets back to Thailand the experts there will attend to the conditions so that one day we will be able to see him walk the normal way,” Ms Perera said.

At the zoo, Muthu Raja’s morning routine has included vet check-ups, bathing in a small pond and practising getting into the container that will carry him on the nearly six-hour flight to Chiang Mai, Thailand.

The container is cushioned and has windows for feeding. His meals will include bananas, pumpkin and sugar cane. Zoo officials have hoisted the 9ft tall, four-ton creature in trial lifts to test the container’s strength.

Muthu Raja will be sedated if necessary and two vets will monitor him during the journey. Three Thai and one Sri Lankan elephant tenders also will be on the plane.

Ms Panapitiya said her group had unsuccessfully tried to raise the issue of Muthu Raja’s neglect with the Sri Lanka government for months before turning to the Thai government, and said the failure of Sri Lankan wildlife officials to act had brought “disrepute” to the country.

Prime minister Dinesh Gunawardena told Parliament earlier this month that he expressed his regret to the Thai prime minister over the treatment of the elephant during a trip to Thailand in May.

Ms Panapitiya said her group is also pushing for the release of another elephant at the Kande Viharaya temple.