The Counter-Corruption Division (CCD) has summoned 10 witnesses to testify in the bribery case involving the chief of the Department of National Parks, Wildlife and Plant Conservation (DNP) after the New Year.
On Tuesday, the department's director-general Rutchada Suriyakul Na Ayutya was arrested on charges of demanding or receiving bribes and malfeasance in office.
CCD commander Pol Maj Gen Jaroonkiat Pankaew said on Friday that police had issued summonses to DNP officials whose names appeared on the cash envelopes found at Mr Rutchada's desk.
Ten of them will now be required to testify to the police in January about the acquisition of such cash, he said.
Pol Maj Gen Jaroonkiat revealed he was confident that the evidence would refute any denials by the suspects that the cash-stuffed envelopes were not bribes exchanged for retaining their positions.
In addition to the DNP suspects, Pol Maj Gen Jaroonkiat said Chaiwat Limlikit-aksorn, the former head of Kaeng Krachan National Park in Phetchaburi, was also summoned as a witness to provide further details about the envelopes in Mr Rutchada's office.
Mr Chaiwat had earlier filed a complaint with CCD police against Mr Rutchada, accusing him of abusing his authority in transferring officials who refused to pay him 500,000 baht to positions far away from their home provinces.
Meanwhile, serial petitioner and activist Srisuwan Janya said he will visit the National Anti-Corruption Commission (NACC) on Jan 3 to request an Integrity and Transparency Assessment (ITA) be imposed upon the DNP.
In the 2022 fiscal year, the DNP was rated "A" for corruption prevention and received a prize-winning score of 100 out of 100, which has surprised some pundits.
While Mr Srisuwan said the prize should be withdrawn, NACC secretary-general Niwatchai Kasemmongkol defended the assessment on the basis that it was the result of participation from both its own staff and the general public.