Col Prawit Suthireunarun, Chief of the Tha Chatchai Police, was notified of the incident at 4:30pm, when he was told that the body of a woman stabbed to death was lying in the street in front of Tha Chatchai Temple, at the northern tip of the island.
Police and rescue workers arrived to find the body of Orathai Fornghoi, 55, lying face up on the ground.
She had been stabbed five times.
Witnesses told police that Ms Orathai had been living together with a man identified as Somboon Saelao, 69, for three months, but the couple had separated about a week ago.
The breakup left Somboon bitter and angry, police were told.
Witnesses told police that Ms Orathai went to a garage in the village near the temple, but when she arrived Somboom was already there.
The two argued, and Somboon produced a knife and repeatedly stabbed Ms Orathai before fleeing.
Police noted that motivation for the attack seemed to be that Somboon was jealous that Ms Orathai may have been seeing another man.
Tha Chatchai Police are checking CCTV from the area in the hope of tracking Somboon down.