Police on Thursday arrested one more suspect in a high-profile case in which serial petitioner Srisuwan Janya and two other parties have already been detained on suspicion of extorting money from Natthakit Khongthip, director-general of the Rice Department.
Eakluck Wareechol, the fourth suspect in this case, was arrested at his house in Khlong Sam Wa district of Bangkok on Thursday morning by a team of police and officials from the National Anti-Corruption Commission (NACC) and Public Sector Anti-Corruption Commission (PACC).
According to the source, three boxes of documents were seized from the suspect's house.
Mr Srisuwan was arrested last Friday at his home for allegedly demanding 3 million baht from Mr Natthakit. His alleged accomplices -- Yoswaris Chuklom, also known as Jeng Dokjik, and Phimnattha Chiraphutthiphak -- turned themselves in later and were released on bail after questioning.
Mr Eakluck is believed to be a key figure in the alleged extortion. He acted as a broker between a man identified only as Mr Mu, who worked with Mr Srisuwan and Mr Yoswaris, as well as with an adviser to a cabinet minister -- neither of whom was named -- said the same source.
The police also searched a house in Uttaradit for another suspect, said the source, adding more details would be revealed later.
Pol Maj Gen Jaroonkiat Pankaew, deputy commissioner of the Central Investigation Bureau (CIB), said Mr Mu was an adviser to Agriculture and Cooperatives Minister Thammanat Prompow.
However, the authorities could not confirm if Mr Mu would be charged for his suspected involvement in the extortion, said Pol Maj Gen Jaroonkiat, adding Mr Mu would be interrogated by the police.
"As more evidence continues to emerge, we cannot yet conclude there are just these five suspects," said Pol Maj Gen Jaroonkiat.
Mr Yoswaris and Ms Phimnattha, meanwhile, organised a press conference to insist on their innocence.
According to Mr Yoswaris, he became embroiled on Dec 18 in a probe into the suspicious procurement plan for a 1.18-billion-baht aircraft by the Department of Royal Rainmaking and Agricultural Aviation (DoRRAA).
When he found that Mr Srisuwan had obtained evidence of the same irregularities, they decided to jointly file a petition to the House committee monitoring the state budget to look into these irregularities, Mr Yoswaris said.
After that, he found that Mr Srisuwan had evidence of suspected corruption within the Rice Department, which matched the document he also had, according to Mr Yoswaris.