The survey, on May 30-June 1, inspected areas at Ao Rang Kai and Ao Banana (Banana Bay) at Racha Noi Island and at Ao Tu and Ao La at Racha Yai Island. The areas are all popular tourist sites.
Coral bleaching was found affecting natural areas such as rocks, branches, glazes, giant clams and pale anemones, said a report by the DMCR.
The affected areas included natural reefs at depths of 3.5-10 metres, and at artificial reefs at depths of 10-13m, noted the report.
The water temperature was recorded at 31°C.
However, the survey team did report seeing two leopard sharks, about 2.5-3m long, in the Kai Rang Bay area, which they took to be a good sign.
Seafarer Divers provided the boat and the diving equipment for officers to conduct the survey, the DMCR noted.
Diving Instructor Thawatchai Jiwsuwan, a volunteer joining the survey, will compile the images and a report to be submitted to DMCR for further consideration, the report said.