The incident occurred around 1:30am at a shop selling bags, headphones and miscellaneous items on Rat-U-Thit 200 Pi Rd. According to Pol Lt Col Chanan Mekchai of the Patong Police, the theft was reported by Ngo Van Binh, a 42-year-old Vietnamese employee of the store.
Mr Ngo stated that the tourist entered the shop with his female companion, both of unknown nationalities, and began browsing. During their visit, the man allegedly stole a pair of headphones. When Mr Ngo noticed the theft, he pursued the couple while shouting for assistance.
A bystander, identified as Chanaphon Soponrat, 31, originally from Phatthalung, responded to the calls for help and joined the chase. However, the suspect reportedly pulled out a knife and slashed Mr Chanaphon in the left arm before fleeing the scene.
Mr Chanaphon was rushed to Patong Hospital, where he is currently receiving medical treatment for his injuries.
Police are now actively searching for the suspect, who remains at large.
Officers are reviewing CCTV footage and gathering witness statements to track down the perpetrator and bring him to justice.