Increases in fees across all 29 national parks in Thailand will mean a small increase in fees for overseas visitors to the Similan Islands and Surin Island, from 400 baht to 500 baht (Thais will pay 100 baht).
The increase in land-based parks will be considerably greater, from 200 baht to 500 baht, with Thais paying 100 baht - up from 40 baht.
The Director of the Similan islands National Park, Mana Permpoon, told Phuketwan today that much of the diving business at the Similans has now moved to Bali.
Russian and Chinese snorkellers had replaced the divers, he said, putting the reefs at greater risk from damage.
''The quality of boats and the wearing of life jackets needs to be checked more frequently now,'' he said.
''The reefs have recovered from the coral bleaching phenomenon of two years ago, but the danger now is damage from tourists.''
Two meetings have been called by Khun Mana in Khao Lak, north of Phuket, for snorkelling operators on August 29 and dive operators on August 30.
Khun Mana said he hoped to make the point that all garbage needed to be carried away with boats, that fuel leaks had to be prevented, and that snorkellers should not stand on reefs.
''Because some of the snorkellers have no experience, they sometimes don't understand that they cannot take pieces of coral as souvenirs,'' he said.
The Department of National Parks, Wildlife and Plant Conservation says some national parks are suffering from too many tourists and the new fees will be a deterrent to help fight environmental deterioration.
Some of the Similan islands are open to tourists from November to April and closed the rest of the year to allow them to recover.
Other islands are kept in natural condition, with one home to a turtle sanctuary.
Rohingya boatpeople have been contained briefly on some Similan beaches in the past so arresting Thai Navy officers can check whether they are armed.
In a policy change, the Navy now ''helps on'' the would-be refugees rather than apprehending them.