Thai police said Swiss national Xavier Andre Justo, who is in custody and expected to be charged with blackmailing his former employer, PetroSaudi, has given a full confession and identified about 10 people who bought documents from him to use to attack Malaysian Prime Minister Najib Razak.
"He has confessed everything. He has given us very good cooperation... every document, even from inside his phone,'' police spokesman Prawuth Thavornsiri told The Straits Times.
Justo sold the data he had taken from PetroSaudi to the group, which included media figures and a person from the Prime Minister's own party, according to Lieutenant-General Prawuth. Among them was a Malaysia-born woman who had moved to Britain.
"She has a news blog," he added.
Asked if the blog was the Sarawak Report website, he said: "Maybe. I didn't name it, you named it.''
He said the website "usually gives bad news about Malaysia".
"The website tampered with the data to discredit the PM,'' he added.
Lt-Gen Prawuth said he could not mention names. But he confirmed that Justo met with "many people, about 10, from the media and from political circles, even from the same party as the PM (Datuk Seri Najib)''. Justo met the Malaysia-born woman three times in Thailand, and also in Singapore, for "negotiation", said Lt-Gen Prawuth.
In the last stage of the negotiations, once the group had verified that Justo's files contained the information they wanted, they discussed how to pay him.
The evidence from Justo included a full transcript of all the Whatsapp chats he had with the group during their negotiations and discussions on how he would be paid. Some meetings are said to have been held in Singapore.
"The way they paid was the same way money-laundering gangs pay, Lt-Gen Prawuth said.
"They talked to each other many times by Whatsapp, we have the evidence; they talked about paying like this and like that, to pretend to buy and sell.''
These details "should be useful" to Malaysian police, he added.
The spokesman also offered to share information with the Singapore police. "This case should be reported in Singapore because the money laundering to attack the PM started in Singapore," he said.
"If the Singapore police ask me for evidence (through) the foreign affairs protocol, I can send it."
Thai police arrested Justo at his plush home on the resort island of Koh Samui on June 22.
The tattooed 49-year-old had worked for PetroSaudi from 2010 to 2011, Lt-Gen Prawuth said.
"The CEO of that company was Xavier's close friend. I don't know what conflict they had; he (Justo) walked out and requested money from the company," he said.
"The company paid him about four million Swiss francs at the time he walked out.
"After two years Xavier called the CEO again and asked for some money again. Before he left, he had copied every e-mail of the company from the server. It was in 2013 that he called the company and said I know all your secrets, and I want US$2.5 million."
When PetroSaudi turned down his demand, Justo then approached the other group, said Lt-Gen Prawuth, who took care not to mention Malaysia by name.
Justo would be charged with blackmail, Lt-Gen Prawuth told The Straits Times. "The blackmail happened in Thailand, so we only have scope for that," he added.
On July 3, the Wall Street Journal and Sarawak Report claimed that US$700 million (S$957 million) linked to 1Malaysia Development Berhad was deposited into Mr Najib's private bank accounts over the past two years.
The beleaguered Prime Minister, who is facing calls for his resignation led by influential former premier Mahathir Mohamad, has denied ever using state funds for "personal gain".
Mr Najib has accused Tun Dr Mahathir, who was Malaysia's prime minister for 22 years until 2003, of conspiring with international media to topple his government via "political sabotage".
1MDB's recent struggle to meet financing obligations, as it seeks to pare down RM42 billion (S$15 billion) in debt it racked up in its first five years of operation, has been a lightning rod for criticism against Mr Najib's leadership.
The state investment agency is now the subject of multiple probes by the Malaysian authorities.
Malaysian police have asked their Thai counterparts for access to Justo but have yet to interview the Swiss national.