Police arrested the gunman hours later at Kalasin Hospital where he had gone for treatment of his wrist injuries, Thai media reported.
The shooting took place in the emergency room of Pak Khat Hospital after a brawl between two groups at a local restaurant, reports the Bangkok Post.
Surichai Sunanthanam, 21, of Nong Khai, was shot dead, said Pol Col Chaiyut Thamsuna, chief of the Pak Khat station. Four bullets from a 9mm pistol were fired at the victim.
Video posted on social media showed an armed man in a blue T-shirt, entering the hospital’s emergency room at 1:20am on Saturday and immediately firing shots at an injured man who was on a gurney, causing panic among two female staff.
After questioning medical staff who witnessed the shooting, police determined the identity of the suspect and sought a warrant for his arrest.
Bunyarit Phonkhan, 21, a native of Pak Khat, is now in custody after his arrest in Kalasin. Chalit Maengthaisong, 20, of Bueng Kan, is also being held on a charge of helping the gunman escape.