Former Olympic marksman Jakkrit Panichpatikum died on Saturday night of gunshot wounds after being attacked as he sat in his car, police said.
Jakkrit was pronounced dead at Serirak Hospital where he was taken after being shot three times with 9mm bullets in his chest and stomach.
The shooting took place while Jakkrit was in his black Porsche in the compound of Wat Bampen Tai on Sukhaphiban 3 Road at around 7.10pm. The window on the driver's side had three bullet holes.
Jakkrit represented Thailand on the national pistol-shooting team at the 2012 Olympics in London. He was out on bail following his arrest on July 13 after a disturbance at his home.
Officers said that in the July incident Jakkrit had fired a gun into the air in his family home to frighten his wife, Nitawadee Pucharoenyos, before assaulting her.
He was charged with attempted murder, assault, illegal possession of firearms and committing violent acts.
The father of two admitted he fired the gun but said he never intended to harm anyone. But his wife and mother said he had a history of violence and that his behaviour had worsened since his return from London.
Pol Col Ek Ekasat, deputy chief of the Metropolitan Police Bureau's Division 3, pointed to drugs, sexual affairs, gambling and personal conflicts as possible motives behind the shooting.
Investigators did not rule out his marital problems but were not convinced that the July quarrel would have led to a revenge attack by his wife.
Police are checking closed-circuit camera footage at the scene and searching for other clues to the shooter's identity, he added.