A drunk policeman ran out of his police flat, kicked over a passing motorcycle and repeatedly stabbed the two riders, killing one of them.
Pol Sgt Chavanil Jindamaneemas, 30, was arrested and sacked after the attack.
The dead woman was identified as Wijitra Rakkhanam, 51, and the seriously injured woman as Prapha Yamyuean, 69. They were stabbed repeatedly in the face, neck and back.
According to police, Chavanil had just been transferred from Phuket and was being treated for tension.
On Saturday evening, Chavanil drove his car into a pit. After a tow truck arrived to pull it out, the driver heard the officer speaking angrily with his mother on his mobile phone. The tow truck driver then told the police sergeant not to scold his mother. Enraged, Chavanil tried to stab him, but the driver was able to run away.
The attack on the women came after the policeman returned to his flat. As the motorbike approached, Chavanil ran out of his door, kicked the bike to the ground and began a stabbing frenzy. Other policemen rushed from the station and arrested the police sergeant.
A blood test found he was under the influence of alcohol.
Both female victims were vendors and normally lived in Songkhla province. They had just returned to Cha-uat district to visit family.
Several relatives went to the police station on Saturday and demanded to see the attacker in a cell. The sergeant told them that he was sorry. The relatives cursed him out loudly before police convinced them to leave the station.
