Pol Lt Col Songwuth Sri-arm led police and a team of rangers from the 33rd Rangers Regiment and administrative officials to examine the scene of attack and interrogate witnesses.
According to the witnesses, at least 15 armed men arrived in front of two houses at Ban Bannang Kuwae in Bannang Sata district. They opened fire at one of the houses with M16 and AK47 rifles.
Dolo Phadung, 66, and his wife Mariyae Phadung, 60, who were sleeping in the house, were hit and killed.
The attackers then set fire to the house, an Isuzu pickup truck, a Citroen CX20 car and a motorcycle.
They also opened fire at another house which belonged to Abdul Rohman Hengdada, 42, a relative of the slain couple. No one else was hurt in the attack.
The wall of the house was riddled with more than 20 bullet holes.
The attackers fled after the attack, scattering metal spikes on the road to prevent them from being pursued during their escape.
Police are trying to establish whether the attack was motivated by personal conflicts or related to the insurgency.