Police were called to a two-storey house in tambon Kob Jao of Bang Ban district on Wednesday evening, where they found the bodies of two men and two women lying face down near one another in a bedroom on the house’s second floor.
All four victims were found on and near a mattress and each was shot one time with an unknown weapon in the back of the head, Ayutthaya Provincial police chief Sermkid Sitthichaikarn said.
Police identified the slain couple as Nattanicha Kijkasem, 37, who was the house owner, and her husband Worawit Wangmanaopitak, 47. The two other victims are Pisanu Pakammoon, 56, and Pakinee Bangkomnet, 42, both natives of Chiang Rai.
Pol Maj Gen Sermkid said police did not find any traces of a fight at the scene and no valuables in the house had been stolen except Nattanicha’s .38 pistol.
Nattanicha's father Chalem Kijkasem, who lives near his daughter, said his daughter did not have a job and her husband had a tented area where he sold second-hand cars.
He told police he heard gunshots about 9 or 10 pm on Tuesday night but did not suspect anything because the couple usually fired shots to ward off dogs that were barking at night.
He only went to check on his daughter on Wednesday evening and found the bodies after he did not hear from her for almost a day.
Mr Chalerm said the man and woman from Chiang Rai were not relatives and probably were his son-in-law’s friends.
Investigators believe there must have been more than two culprits in the house so that they could force all the victims to lie face down before assassinating them. They are focusing their investigation on personal conflicts stemming from both legal and underground businesses as well as illegal drugs as Pisanu and Pakinee were from Chiang Rai’s border area, Pol Maj Gen Sermkid added.