Justice Minister Tawee Sodsong has confirmed that DSI officers were recently in Amnat Charoen province to investigate Senate election collusion, while former candidates claim imposters have been posing as officers there and coercing them into admitting guilt.
The minister's comment came after provincial governor Narong Thepsena submitted a letter to the Interior Ministry's permanent secretary on Monday, claiming three men posing as DSI officers pressured two female candidates to admit to collusion. The former candidates are Phaiwan Kaewphuang, 57, and Bunlom Wannaphat, 65.
The men claiming to be DSI officers reportedly visited Ms Phaiwan's house dressed not in official uniform and without any state ID on May 4. They disconnected her CCTV camera system and allegedly coerced her into confessing to vote-rigging in the Senate election. When she repeatedly asked what agency they were from, the men failed to answer, she said, prompting her to refuse to cooperate.
A similar encounter occurred with Ms Bunlom, who said she was approached by the three men seeking information about the election.
Pol Col Tawee said investigators had been deployed to Amnat Charoen, where they interviewed more than 10 witnesses.
The DSI was also informed of the incident, he said. He confirmed the three men were DSI officers.
The governor's letter is being reviewed, as under Section 22 of the Special Case Investigation Act, governors are obligated to cooperate in special cases or face legal penalties, including prison terms ranging from one to 10 years.
Pol Col Tawee said he had not received any report from the governor about witness intimidation and encouraged him to report any such incidents to him.
He said the DSI travelled to Amnat Charoen at the witnesses' requests, as they feared the intervention of local influence and claimed to lack the funds to travel to Bangkok.
Regarding the ongoing vote-rigging probe, DSI investigators and the Election Commission (EC) have questioned over 30 witnesses and analysed connections between various groups, suspicious financial transactions of at least 500 million baht at the district, provincial and national levels, and voting patterns and irregular ballot counts.
Evidence has been submitted to the EC, which may revoke the rights of any senators found to be involved.
If wrongdoing is confirmed, cases will be submitted to the Supreme Court's Criminal Division for Political Office-Holders.
The DSI is also pursuing investigations into money laundering and other criminal activities.