Panthongtae "Oak" Shinawatra is again seeking "justice", asking the Department of Special Investigation to reconsider its refusal to take testimony in his defence from additional witnesses in connection with the Krungthai Bank (KTB) loan scandal case.
His lawyer Chumsai Sriyaphai made the request in a petition for justice submitted to DSI chief Pol Col Paisit Wongmuang.
Mr Chumsai said DSI investigators refused to take testimony from 10 defence witness added to the list, putting his client at a disadvantage.
These witnesses were "crucial to the accused in proving his innocence", Mr Chumsai said.
The Anti-Money laundering Office (Amlo) has accused Mr Panthongtae, the only son of fugitive Thaksin Shinawatra, and three other suspects with laundering money by receiving cheques worth 10 million baht and 26 million baht tied to wrongfully approved KTB loans.
The KTB scandal involves 9.9 billion baht in loans the bank grated to subsidiaries of the Krisdamahanakorn (KMN) real estate company during the Thaksin administration even though the firm was listed by the bank as a non-performing debtor.
Mr Chumsai, in September last year, first sought justice in the case by asking the DSI not to accept the allegation filed by Amlo for consideration, arguing that it lacked clear evidence. However, the DSI decided to push ahead with the case.
Mr Chumsai now alleges an irregularity then erupted during its continuing inquiry. He suspected a "special power" may have interfered with the investigation, allegedly lead to the rejection of the witnesses.
Pol Col Paisit said DSI was willing to question all witnesses, but the investigators were careful to accept only those who had new information to give, not people repeating testimony already given by others.
He said some witnesses also delay the case, asking investigators for postponements in giving their accounts.
The DSI planned to finish its investigation this month and wrap it up before the statute of limitations in the case expires in June this year, he said.
Lawyer Chumsai also petitioned the Office of the Attorney-General on Mr Panthongtae's behalf on Wednesday. He sought the investigation and suspension of Kajornsak Phutthanuphap, deputy executive director for interrogation, accusing him of questioning only eight of 20 additional defence witnesses.
Mr Kajorn said Mr Panthongtae had wanted another 20 witnesses to give evidence, and the statute of limitations in the case was fast approaching.
He had already accepted eight witnesses, and Mr Panthongtae had also postponed their interrogation. Additional witnesses could be proposed in court during the trial, Mr Kajorn said.