Tony Kenway, 39, originally from Southampton, who was married to Pans Kenway, 32, was shot dead while sitting in the driver’s seat of his red Porsche Cayenne GTS.
He was shot about 2.10pm today (5.10am GMT) in a parking lot in Pattaya, witnesses told police.
Police are investigating links to Mr Kenway and foreign ‘boiler room’ gangs in Pattaya.
The father-of-four, originally from Southampton, was shot dead while in his Porsche
Police collected a single bullet cartridge case and a cigarette butt from the crime scene for examination, the Bangkok Post reported.
According to reports, Mr Kenway had walked from a shop to his sports car and sat in the driver’s seat.
The gunman then went over to the car, pulled open the door and fired a single shot at his head.
He then ran off to a waiting motorbike with a registration number plate 7992 and sped away.
Paying tribute to her older brother, his sister Kirsty Kenway, 31, told MailOnline: ‘I don’t really know what happened to my brother. He’s been in Thailand for years and he’s been happily married for five years.
‘We speak quite regularly and I visted him over Christmas. He had a brilliant life out there and he did a lot for charity, and helped build some schools. He had even met the future King of Thailand.
‘He did a lot of work in IT and was a big fan of sports fans, he was a petrol head.
‘Pans [his wife] is brilliant and she was the light of his life.
‘I was the baby sister [in our family] and he protected me from everybody.’
Mr Kenway’s wife, Pans, 32, told police her husband had set up a website design company.
He recently had a business conflict with a shareholder, but she did know if that was the motive for the murder, the newspaper reported.
The killer was a tubby man, wearing a white T shirt, black jacket, sports shoes and a baseball cap.
Pattaya is a city on Thailand’s eastern Gulf coast known for its beaches.
An FCO Spokeswoman told MailOnline: ‘We are in contact with the family of a British man following his death in Pattaya, Thailand.
‘Our sympathies are with them at this difficult time. We are in touch with the local police.’
A spokesman for Nong Prue Police in Pattaya said: ‘We have started an investigation and we are looking for the attackers.
‘The victim has been identified as Tony Kenway, a 39-year-old man from England. We are speaking with more witnesses.’