Police General Hospital Director Pol Lt Gen Jongjate Aojanepong said on Friday that the forensic examination showed that the two skeletons did not match Samart Noomjui and Orasa Kerdsap, who went missing in 2009.
Pol Col Supat, a former doctor with the hospital, is suspected of murdering the couple, as well as two Myanmar migrant workers employed at his pineapple orchard.
A forensic examination conducted by the hospital's Institute of Forensic Medicine on the first skeleton on Thursday showed that it was a male, about 168 to 172 centimetres tall, who died more than a year ago, said the hospital director.
The inspection of the first skeleton's teeth suggested he was 17 or 18 years old when he died, said Pol Lt Gen Jongjate, adding that the identity of the remains as well as the cause of his death has yet to be verified.
The forensic team established that a second skeleton belonged to a male about 169 to 174cm tall, and 40-50 years old at the time of death. He is believed to have been killed by a gunshot to the head, based on a hole found in the skull, Pol Lt Gen Jongjate said.
The police forensic team could not determine the sex of the third skeleton examined because the remains were incomplete and too badly decayed. Based on a dental examination, forensic experts estimated the age of the third body was 18 to 19 at the time of death.
The team also found that the second and third suspected victims died more than one year ago. The accuracy of the age estimates is about 99% certain, the team said.
It is highly unlikely that the second and third skeletons are Mr Samart and Ms Orasa, who were both between 26 and 27 years old when they disappeared, police said.
Sawang Noomjui, Mr Samart's father, said he was dismayed by the DNA test and forensic examination results.
He called for another forensics team to test the skeletons again, as he firmly believes that one of the skeletons is that of his son.
Previously, Mr Sawang had said that his son's dark blue T-shirt was found on the skeleton and it had a tooth missing in exactly the same spot as his son.
Pol Maj Gen Juti Thammanowanich, a deputy commissioner of Provincial Police Region 7, said police investigators will meet to consider the forensic and DNA testing results and are expected to press a charge of premeditated murder against Pol Col Supat.
Even though the bodies of Mr Samart and Ms Orasa were not found, police now have solid evidence to charge Pol Col Supat with their murder, said Pol Maj Gen Juti.
Pol Maj Gen Juti also confirmed that Suthep Laohawattana, the brother of Pol Col Supat, yesterday met investigators for questioning regarding the murder case.
However, the brother requested that his privacy be protected from the media.
Mr Suthep did not want the public to know when and where he would meet the investigators yesterday for security reasons, said Pol Maj Gen Juti.