The attack occurred about 9.15am on the Bannang Sata - Bannang Kuwar road near Ban Tao Pun in tambon Bannang Sata.
Witnesses told police that Apichart Saengchan, 24, and his wife Angkhana Noodaeng, 22, were travelling on a motorcycle from Ban Busu, heading for Muang district. Two men in black followed them on another motorcycle.
The two opened fire at the couple with handguns.
Apichart was hurt in the fall from the motorcycle while Angkhana was hit by several bullets. She was rushed to Bannang Sata Hospital where she was later pronounced dead.
Police recovered five spent 9mm gun shells at the scene.