After announcing it will close down Koh Tachai in Phang Nga province indefinitely due to negative effects on the environment, Thailand's Department of National Parks, Wildlife and Plant Conservation (DNP) says it will block access to a further 14 diving spots in Southern Thailand.
Thanya Nethithammakul, Director General of DNP, said a recent survey of eight national marine parks revealed 40-80 percent of coral reefs show signs of bleaching. 
The affected spots, located in both the Gulf of Thailand and Andaman Sea, are as follows: Koh Yung of Hat Noppharat Thara-Mu Ko Phi Phi National Park, Krabi province; Koh Maphrao, Koh Ngam Yai, Koh Ngamnoi and Koh Kula of Mu Koh Chumphon National Park, Chumphon Province; Koh Talu and Koh Kuthi of Khao Laem Ya-Mu Ko Samet National Park, Rayong Province; Koh Ayam, Koh Rung and Koh Buloan Mai Phai of Mu Ko Phetra National Park in Satun province; Tarutao National Park in Satun province; Mu Ko Lanta National Park in Krabi province; Koh Tachai of Mu Ko Similan National Park; and Mu Ko Surin National Park, the best shallow coral in Phang Nga Province.
While all marine national parks are closed from May 15 to Oct 15 for the monsoon, Koh Tachai and the above-mentioned spots will remain closed indefinitely. 
Koh Tachai, part of Similan National Park, was originally designated as a primitive zone, meaning preserved for important or sensitive natural resources. But since welcoming unregulated tourism two years ago, the island has quickly deteriorated under the weight of up to 1,000 visitors a day. The latest survey reveals extensive damage to 70-percent of coral reefs. 
Koh Tachai is the only place in Thailand that's home to a rare form of blue coral, and it's also home to a newly-discovered species of green emerald snails that can’t be found anywhere else in the world.