The charges stem from the abduction and murder of a brother of a senior judge to force her to drop an indictment against Pol Lt Col Banyin in a share transfer case.
Wirachai Sakuntaprasoet, an elder brother of Bangkok South Criminal Court judge Phanida Sakuntaprasoet, was kidnapped by four men outside the court on Feb 4. The 70-year-old was later killed and his body burned and dumped into the Chao Phraya River in Nakhon Sawan.
One of the alleged kidnappers was Pol Lt Col Banyin, who drove Wirachai from Bangkok to a wood in Khao Bai Mai in Nakhon Sawan, police revealed on yesterday (Feb 24).
Pol Lt Col Banyin and two aides alleged accomplices, Manat Thapnin and Narongsak Pomchan, were arrested on Sunday (Feb 23).
Questioning of Mr Manat led to the arrest of three more suspects, identified as Pol Senior Sgt Maj Thongchai Wachisatcha, Prachawit Sithongsuk and Chatchai Menkun.
All were initially charged with threatening a state official, illegal assembly, demanding a ransom and abduction.
Police added premeditated murder and conspiracy to detain a person, resulting in his or her death to the charges following the discovery of bloodstains in one of four seized cars and bone fragments believed to belong to Wirachai, a police source told the Bangkok Post.
Investigators found the fragments, damaged car tyres and shirt buttons where the victim was supposedly burned.
What was left of his body was stuffed in fertilizer bags which were then dumped in the river, according to investigators.
Divers were trying to retrieve the bags near Takhian Luean Bridge in Nakhon Sawan’s Muang district.
The crime was well planned as the suspects registered new mobile phone numbers and attached fake registration plates to their cars, said one police officer.
Pol Lt Col Banyin, who is still in custody, denied the charges.
The alleged crime took place as a March 20 ruling on his share transfer case draws near. He was accused of forging documents to set up the transfer of B300 million worth of shares owned by his friend and businessman Chuwong Sae Tang, who was killed in a road accident in a car driven by Pol Lt Col Banyin in 2015.