Suphakit Kei-Suniun, 38, was rushed to hospital bleeding from his jugular artery, and died soon after.
The investigators were told that a group of teenagers were having a party outside rented rooms in Soi Thanitturakit 4, off Sakdidej Rd.
Mr Suphakit rode up on his motorbike, straight at one of the revellers, whose name witnesses were unable to supply.
The two argued fiercely and Mr Suphakit’s opponent jumped to his feet, pulled a gun and shot as Mr Suphakit but missed him. He then walked up close to his opponent and shot at him again, this time hitting him in the neck. After that he ran away.
Investigators believe that Mr Suphakit may have come to demand repayment of a loan, and this had infuriated the gunman.
At the scene investigators found broken beer and whisky bottles on the ground, a Black Honda motorbike lying on its side with a pool of blood nearby. They also found a .38-calibre bullet casing on the ground.
Police are now trying to track down the gunman.