BANGKOK: Thailand will this month release jailed Swiss national Xavier Justo, a possible key witness in the global money-laundering probe linked to Malaysian state fund 1Malaysia Development Berhad (1MDB), after he was granted a royal amnesty for a fraud conviction, his lawyer said on Wednesday.

Justo leaked several confidential documents from his employer Petrosaudi International relating to its joint venture with 1MDB that were published by Malaysian and international media groups early last year and formed the basis for the money laundering probe.

Justo was among 150,000 Thai and foreign inmates who were pardoned or had their sentences commuted by Thailand's new King Maha Vajiralongkorn as the first act of mercy since he ascended the throne earlier this month.

Founded by Malaysian Prime Minister Najib Razak, who chaired its advisory board, 1MDB is the subject of money-laundering investigations in at least six countries including Switzerland, Singapore and the United States.

Justo, now a former employee of Petrosaudi, a Saudi Arabia-based oil and gas company and former joint venture partner of 1MDB, was arrested by police on the Thai island of Koh Samui and was jailed for three years in August 2015 after being found guilty of blackmailing Petrosaudi.

His sentence was cut by a royal amnesty in August, prompting Swiss authorities to request his transfer to serve the remaining term back home.

Justo's lawyer in Thailand, Worrasit Piriyawiboon, said Justo would likely be released before Dec. 25.

"The first lot of Thai prisoners will be released on Dec. 15 and foreign prisoners will be released seven to ten days later," Worrasit told Reuters, adding that Justo met the conditions for a royal pardon because he had less than one year of his prison term left.

"Following his release he will spend some time at an immigration detention centre in Bangkok and will then be sent to Switzerland," said Worrasit.

"All foreign prisoners must be supported by their embassy."

Reuters was unable to reach the Swiss Embassy in Bangkok for comment.

Malaysia last month rebuffed Switzerland's request for legal assistance in probing suspected corruption linked to the scandal-hit state fund.