A man has confessed to killing a couple and their 18-month-old daughter before setting fire to their house to conceal the murders, police said on Friday.
Pol Gen Suwira Songmetta, a police inspector-general, said after interrogating Niphon Changkaew that the 38-year-old man had admitted to shooting to death Samran Phetprdap, his wife Rungthip Saithong and their child in Sam Roi Yot district of Prachuap Khiri Khan on Wednesday.
The suspect then torched the house to make it appear that the three had died in the blaze, the officer said.
Mr Niphon, who worked on the shrimp farm that the family ran on the property, reportedly said money was the reason for the murders. He claimed he had not received his salary of 8,000 baht for the first three months as he had been promised, and the rest was not paid on time.
Officers from the Sam Roi Yot police station found the one-storey house burned to the ground on Wednesday, with the charred remains of three bodies inside. The case became a murder investigation after autopsies found that all the victims had been shot in the head by an 11mm pistol.
The bullet shells, a five-litre gasoline canister and pools of blood substantiated their theory, leading to the arrest of the suspect on Wednesday night.
Pol Gen Suriwa said a pool of blood would not normally be found at a site where people have died in a fire.
Police also found three tanks containing 200 litres of benzine about 20 metres from the burned house and collected fingerprints as possible evidence. An 11mm gun was also found near the crime scene.
Forensic investigators are now checking whether the bullets and the pistol are a match.