Krabi tourist police arrested the Thai owner of a tour business on Friday after his foreign clients damaged coral while snorkelling off Phi Phi Island.
Pol Lt Col Atthapong Saenjaiwut said Nipon Midsae, 34, was charged with running a tour business without a licence.
Conviction could result in a jail term of two years and a fine of Bt500,000.
The arrest came after a foreign tour guide took other foreigners on a snorkelling expedition to the Viking Cave near Phi Phi Island earlier this week, where the coral was damaged.
Marine park officials fined the owner of the boat Bt1,000, Atthapong said, but Nipon refused to identify the foreigner in charge, so police scrutinised his documentation and found he had no business licence.