The gunfight between two young men happened in front of a noodle shop on Ban Kok road in Tambon Ban Ped of Muang district.
Komphet Nakwaen, 19, was killed at the scene and his girlfriend was shot in her arm and sent to Khon Kaen Hospital.
Police are checking with clinics to see if they have treated a young man shot in his abdomen.
Witnesses told police that Komphet stopped his motorcycle in front of the noodle shop before two other motorcycle arrived. A motorcyclist was seen walking over to talk to Komphet and then pulling out his gun.
Komphet was seen pulling out his gun and firing at the other man, hitting his abdomen, before he then returned fire, killing Komphet and injuring his girlfriend. The injured man fled the scene.