The police have told political activist Srisuwan Janya and two government politicians that they have 15 days to provide documents to defend themselves against accusations of extorting money from the Rice Department (RC) chief.
Pol Maj Gen Jaroonkiat Pankaew, deputy commissioner of the Central Investigation Bureau (CIB), said on Saturday Mr Srisuwan, as well as United Thai Nation (UTN) Party member Yoswaris "Jeng Dokjik" Chuklom and UTN former MP candidate Phimnattha Chiraphutthiphak, have asked for more time to prepare their rebuttals against the charges, brought on Friday, which they have all denied.
He said the documents will need to be presented to investigators within 15 days. In the meantime, Mr Srisuwan and the UTN members have refused to give further verbal statements.
After lengthy questioning by police on Saturday, the three were each granted bail, of 400,000 baht each.
If any state officials are found to have taken part in the alleged extortion, the anti-corruption police will launch a probe and alert the National Anti-Corruption Commission (NACC), he said.
Pol Maj Gen Jaroonkiat said no one else is implicated in the case so far. However, investigators have discovered proxy bank accounts alleged to have been set up to receive extortion money.
Police are widening the probe as they believed the extortion plan may have been the work of a team consisting of a petitioner, a go-between, the owner of the proxy bank accounts and a courier who picks up the money from the blackmailed party.
Pol Maj Gen Jaroonkiat said police spent four months gathering evidence on the case. At least one more person will be summoned to give a statement today.
After police questioning, Mr Srisuwan said he was unperturbed by the legal action and vowed to continue with the whistle-blowing work he is known for.
Mr Srisuwan is accused of banding together with Mr Yoswaris and Ms Phimnattha to extract money from RC director-general Natthakit Khongthip.
The three allegedly demanded a bribe of 3 million baht, which was later dropped to 1.5 million baht following negotiations.
Mr Natthakit, who told police he had done nothing wrong, said he agreed to pay the first instalment of 500,000 baht because he wanted to gather evidence of the bribe attempt.
Mr Natthakit had promised to hand Mr Srisuwan the money which the police unit recorded being delivered to Mr Srisuwan's house in Lam Luk Ka district on Friday.
In the police's sting operation, Mr Srisuwan's wife was seen emerging from the house to collect the bag of money hung on the front gate.
According to Pol Maj Gen Jaroonkiat, she ran with the money to the back of the house, prompting officers to move in. Police found Mr Srisuwan in the house and inquired about the whereabouts of the money.
Mr Srisuwan led the officers to the stash of cash thrown over the fence to the neighbour's house. Police discovered Mr Srisuwan installed CCTV around his house and investigators were reviewing the footage from the cameras, Pol Maj Gen Jaroonkiat said.
"Mr Srisuwan is in a very sticky situation," the deputy commissioner said.
Mr Srisuwan denied extorting anyone. He explained that after his wife had shown him the money in the bag, he had no idea where it came from, and decided to discard it somehow by tossing it into the neighbour's house.
"I've no doubt I've been framed by someone who has lost power or been subject to legal investigation as a result of my relentless pursuit to hold public office-holders to account for almost 10 years.
"They are trying to take me down. But I have information to counter the allegation levelled against me," he said, vowing to continue his whistle-blowing quest.
Mr Srisuwan insisted he was not shaken up by the arrest. "To be doing what I've been doing is like walking in the rain. One is bound to get soaked," he said.
Meanwhile, UTN leader and Deputy Prime Minister Pirapan Salirathavibhaga said the party reserved the right to expel Mr Yoswaris if the investigation confirms he had a hand in the alleged extortion, or he could offer his resignation.
The deputy premier maintained the allegation had nothing to do with him or the party.
Yoswaris: Faces UTN probe into involvement
Phimnattha: Former UTN MP candidate