A manhunt has been launched for four suspects, including a kamnan in Ratchaburi province, in the love triangle murder case of a young woman.
The arrest of the kamnan and three other suspects would help investigators gather enough evidence to prosecute the person police suspect was the mastermind, a police superintendent in Ratchaburi.
The gang allegedly abducted Suphakson Ponthaisong, 28, who was found buried in neighbouring Kanchanaburi province's Muang district on Wednesday, police said.
Pol Col Amnuay Phongsawad, 58, superintendent of Ban Pong district police station, was arrested for allegedly hiring the kamnan to manage the abduction of Suphakson.
The kamnan was believed to have later contacted Niwat Suaythong, 32, to complete the job.
The motive for the killing is still unclear. According to police, there are two motives being investigated.
The first is believed to be jealousy, as the victim allegedly had a secret romantic relationship with Kannikar Krumrum, a 38-year-old restaurant singer who is allegedly a mistress of Pol Col Amnuay.
The second concerns a 4-million-baht debt Suphakson allegedly owed Ms Kannikar. The money belonged to Pol Col Amnuay.
Ms Kannikar, another suspect, was also detained as she is believed to have lured Suphakson in preparation for the abduction.
Police investigators said the kamnan, in fact, did not want to do the job, but he allegedly introduced Mr Niwat, his aide, to Pol Col Amnuay.
Mr Niwat, together with his alleged accomplice Phumithat Piboonsawad, 24, are being detained by police. Both allegedly confessed to Suphaksorn's abduction, according to Metropolitan Police Bureau chief Sanit Mahathavorn.
City police have joined the investigation after investigators found Suphakson had been abducted near her apartment in Phetkasem Soi 116 in Bangkok's Nong Khaem district.
According to an investigation and a CCTV footage, Mr Niwat drove a pickup truck to cut in front of a motorcycle ridden by Suphakson.
She fell and was put into the pickup by two suspects -- Phanumet Meela, 34, and Lt Chaiyuth Benjachart, 41. Mr Phumithat was also in the truck.
Suphakson was held in a vacant resort in Kanchanaburi where suspect Samart Saegnsin, a former police officer, was hired to take care of her, investigators said.
Pol Lt Gen Sanit yesterday told investigators to speed up the arrest of the three suspects -- Lt Chaiyuth, Mr Phanumet and Mr Samart -- who are still at large.
"We'll keep on hunting them," Pol Lt Gen Sanit said. "They cannot escape."
The victim later died of asphyxiation, according to an autopsy conducted by the Institute of Forensic Medicine, following the discovery of her buried body at the deserted resort in Kanchanaburi's Muang district.
However, a source at the institute said yesterday the autopsy did not find evidence that Suphakson had been raped despite the fact that her body was naked when it was found.
Lt Chaiyuth is an officer attached with the 9th Infantry Division in Kanchanaburi's Muang district while Mr Samart is a former police officer and an influential figure in the same district, Pol Lt Gen Sanit said.