The Thai man, Eusob Khonsurin, 23, from Ranong, has been charged with theft, confirmed Capt Samaan Promhorm of the Chalong Police.
Capt Samaan noted in his report that officers were called to the beach at around 11:40am.
On arrival at the beach, officers were met by lifeguard Nara Ratthanarak, 44, and the victim, a foreigner named by police as Morris Graham Parker – together with Eusob.
It was explained to Capt Samaan that Mr Parker had left his bag on the beach, and when he returned found it was gone.
He asked Mr Nara for assistance, and both men began searching for the bag, and questioning other people at the beach.
They met Eusob sitting near the beach. Believing he was acting suspiciously, they challenged Eusob as to whether he had stolen the bag.
Eusob did not answer and walked away to a blue Honda Click parked nearby.
Mr Nara and Mr Morris walked after him and ordered him to show them the storage area under the motorbike seat. Eusob obliged without any argument, and the bag was found there.
Eusob confessed that he had stolen the bag, leading Mr Nara to call the police, Capt Samaan noted.
Mr Eusob was taken to Chalong Police station and charged with theft, Capt Samaan confirmed.
Mr Parker’s black Adidas bag, his driving license, a pair of Playboy sunglasses and B220 cash were recorded as evidence, Capt Samaan noted.