After Samart Noomjui and Orasa Kerdsap, both 27-year-old pineapple farmers, went missing with a Toyota pickup truck, their relatives filed a police complaint about their disappearance on June 17, 2009.
The victims' families believed both of them were murdered and police later identified Pol Col Supat Laohawattana, a doctor at Police General Hospital, as a suspect in the case.
Pol Col Supat reportedly had an argument with the couple before they went missing.
The couple's vehicle was spotted recently at the house of Pol Col Supat's relative in Nonthaburi province.
Hanpol Nitwibun, commissioner of the Provincial Police Region 7, yesterday led more than 100 police officers to examine Pol Col Supat's pineapple orchard in Phetchaburi and found two sacks buried about two metres deep at the place.
The search was conducted after a tip-off by a witness that the remains could have been buried there.
One sack contained bone remains from skull to hip, along with a jacket, while another held leg and feet parts, Pol Lt Gen Hanpol said.
All bone pieces can be combined to form a human's skeleton about 160 centimetres high, the police said.
Forensic examinations will be conducted to match the bones with the missing couple, and the result is expected to be known within three days, he said.
Police will excavate the area again today to find more evidence. The skeletons have not yet been proved to be linked with the disappearance case, Pol Lt Gen Hanpol said, adding that Pol Col Supat will be summoned for questioning.
Police said they also found 42 guns in the suspect's house.
They have yet to contact the suspect to bring him in for questioning.