PETALING JAYA (THE STAR/ASIA NEWS NETWORK) - Former PetroSaudi executive Xavier Justo allegedly met several opposition leaders and the owner of a media group prior to his arrest, according to a Malay daily.

Quoting a source, the Utusan Malaysia newspaper said Thai police had received confirmation that a clandestine meeting took place at the Fullerton Hotel in Singapore.

"Thai police have received confirmation from their Singaporean counterparts that there was a secret meeting between Justo and several individuals from the Opposition, as well as the owner of a media group.

"In fact, the Thai police have admitted that these individuals were involved in stealing, falsifying, and altering the PetroSaudi documents," the source was quoted as saying.

Justo, a former IT executive at PetroSaudi, was arrested by Thai police on June 22 over charges of attempting to blackmail his former employer by threatening to publicly release documents on the company's dealings with the troubled state investment fund 1Malaysia Development Berhad (1MDB).

He was picked up at an island near Koh Samui after PetroSaudi lodged an official report with the authorities.

The documents and email exchanges, which were allegedly "creatively altered", were subsequently published by several local news organisations.

On Friday, Thai police said that Justo had been placed under tighter security to prevent any attempt by outsiders to dissuade him from cooperating with the investigations.

Royal Thai Police spokesman Prawuth Thavornsiri was quoted by Bernama as saying that only certain people were allowed to visit the detainee, who would have security personnel present around him at all times.

Rumours had earlier swirled of an attempt to poison Justo, which the Thai police denied.