Two Japanese men are prime suspects in the murder and dismemberment of their compatriots whose remains were found in Nonthaburi province last week.
An investigation began after a 10-year-old boy spotted a human hand in a bush in Soi Chat San Sawing 2 off Ban Kluai-Sai Noi Road in tambon Pimolrat in Bang Bua Thong district on Friday.
Nonthaburi Provincial Police and Bang Bua Thong Police later discovered decaying parts of the body, including a skull and bone joints, in several black plastic bags scattered along bushes in Soi Phu Yai Liam again on Tuesday.
A source said a gunshot hole was found on the skull.
Police began their search for the two men after a 30-year-old Thai suspect, identified as Kritsakorn Jaiphitak, was arrested on Tuesday night.
The man admitted that he had been hired by three Japanese men as a chauffeur to take them to a factory in the Phutthamonthon Sai 2 area.
The three men were later identified as Suzuki Hiroto, 33, Kato Takuya, 50, and Kabashima Ryosuke, 47 -- the deceased.
Mr Kritsakorn told police Ryosuke sat next to him in the front passenger seat while Mr Hiroto and Mr Takuya took the back seat.
He did not understand what they had talked about but he could sense the three had an argument while he was driving.
They told him to head to a warehouse in Bang Bua Thong in Nonthaburi.
When the car reached its destination, the two men told him to leave the vehicle, which he did, taking a smoking break. He told the police the men were arguing in the car. He later heard a gunshot.
Rushing to the scene, he saw Ryosuke's body on the ground with blood rushing from his head.
He said the two Japanese men took the body to dismember it in the factory and then returned to the car with black plastic bags. He was ordered to dump the bags in many spots in the Bang Bua Thong area, he claimed.
Mr Kritsakorn initially faces a charge of colluding in concealing a body, said Pol Col Parit Chamroonsat, superintendent of Bang Bua Thong Police.
After the interrogation, Pol Col Parit instructed the police investigation team to gather all evidence to seek the court's order for arrest warrants against the two Japanese suspects.
A background check indicated they are Yakuza, based on some tattoo art found on the dead man's hand, Pol Col Parit said.
Mr Hiroto and Mr Takuya are also wanted in Japan, he added.
Immigration Police were instructed to work with Interpol to arrest the two suspects on a murder charge. They are believed to still be on the run in Thailand.
Investigators also learned that one of the suspects is the second in command of a Yakuza gang and has been staying in the kingdom for a long time.
His visa was revoked in 2022 and he is wanted by Japanese police. Officers said the gang is also involved in a call centre scam.