The newspaper cites witnesses who said that an argument broke out between two groups of Thai youths at Zoom Bar on Haad Rin Beach.
A member of one of the groups reportedly fired a shot into the crowd as he ran out of the bar, hitting Mr Ashton in his torso.
Police have reportedly arrested a 26-year-old suspect and plan to question him at Noon on Wednesday.
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A very unsettled start to the new week with heavy, thundery, occasionally wintry showers spreading in from the west throughout the day.