Police apprehended Pol Col Supat Laohawattana at a resort in Puk Tian beach in Cha-am district at about 7pm yesterday, just hours after the third corpse buried in his orchard in Tha Yang district was found and after a court approved an arrest warrant for him and his partner.
Hanpol Nitwibun, commissioner of Provincial Police Region 7, said police tracked down Pol Col Supat from his mobile phone signal.
"The doctor didn't resist the arrest," Pol Lt Gen Hanpol said, adding that the suspect initially denied involvement in the disappearance of Samart Noomjui and his wife Orasa Kerdsap.
The couple, who were employed by Pol Col Supat, went missing in 2009.
The doctor said he had been hiding in several places after learning he was wanted by police. On Friday night, he drove from a hideout in Bangkok to the resort and hid there until police found him.
Pol Col Supat was brought to Provincial Police Region 7 headquarters in Nakhon Pathom province. The interrogation continued until late last night.
In a brief interview with the media before he was questioned, Pol Col Supat insisted he was innocent and that he would only testify to a court.
Kala, a Myanmar worker who is a key witness in the case and located the spots where the bodies were buried, has accused the 57-year-old doctor of torture, but Pol Col Supat said the worker's accusation was groundless.
"I have a record of medical treatment [for the injured worker]," he said.
On Friday, the Myanmar worker, who has worked for Pol Col Supat for more than 18 years, told police that two years ago he witnessed the doctor force a Myanmar worker to take his own life by drinking insecticide.
Kala also claimed he saw him shoot dead another worker. He said he was forced to bury the bodies in the orchard.
Police continued to search the orchard yesterday and found a skeleton believed to be that of a man at the same spot where the second skeleton was found on Friday.
Both skeletons had a bullet hole in the skull, forensic police officers said.
The second skeleton was believed to be the remains of Samart Noomjui, whose father Sawang Noomjui, 55, said it must be his son because he was certain that the dark blue T-shirt found on the skeleton was that of the son.
The skeleton also had a missing tooth in exactly the same position as that of his son, Mr Sawang said in tears.
The first skeleton was dug up on Thursday in a nearby area.
About 50 handguns and rifles have also found and seized during the police search at the suspect's house.
Prior to the search, Mr Sawang had lodged a complaint with Nonthaburi police after the pickup truck belonging to his son and daughter-in-law was found in a deserted house in Nonthaburi that was later identified as belonging to a relative of Pol Col Supat.
Tha Yang district's Tha Mai Ruak police investigators summoned Pol Col Supat for questioning on Friday, but the doctor failed to show up.
The police then sought an arrest warrant for Pol Col Supat and his partner, Wissa Jantharabancha, on unlawful detention of others. The court approved the warrants yesterday.
Police are still hunting for Ms Wissa, who is the caretaker of the orchard. Police said they had found evidence to link the woman to the disappearance of the couple.
Prior to the arrest of Pol Col Supat, a team of police officers searched his clinic on Phetkasem Road and found the doctor's son, Ake Laohawattana.
Mr Ake told police his father occasionally came to the clinic and that he did not know his father's whereabouts.
Police General Hospital director Jongjate Aojanepong said Pol Col Supat had applied for early retirement this year and had been on leave since Sept 3.
The hospital management has already approved his early retirement request, which is still pending final approval from the Royal Thai Police headquarters.
Pol Col Supat had been working at the hospital for about 30 years and he had no problem performing his duty, he said.
However, the hospital management will hold a meeting tomorrow to discuss Pol Col Supat's case as the incident has affected the hospital's reputation, he said.