An idyllic island that is considered one of the most beautiful destinations in Thailand is being shut down — because tourists have wrecked it.

Koh Tachai, an island off the coast of southern Thailand known for its stunning coastline and coral reefs, will be closed indefinitely from October 15, Thai authorities say.

And because the island is already closed due to monsoon season, it’s effectively a no-go zone from now.

Tunya Netithammakul, director general of the department of national parks, wildlife and plants conservation said Koh Tachai needed a chance to recover from damage caused by tourism.

“Thanks to its beauty, Koh Tachai has become a popular tourist site for both Thai and foreign tourists. This has resulted in overcrowding and the degradation of natural resources and the environment,” he told the Bangkok Post.

 “We have to close it to allow the rehabilitation of the environment both on the island and in the sea without being disturbed by tourism activities before the damage is beyond repair.”

Authorities are now warning tourists not to be fooled by tour companies trying to sell trips to the island after October 15.

Environment expert Thon Thamrongnawasawat told the Bangkok Post the island couldn’t cope with the huge numbers of tourists it attracted.

“In fact, Koh Tachai is preserved as a primitive zone, not a tourist site,” Mr Thamrongnawasawat, the deputy dean of the Faculty of Fisheries at Kasetsart University, said.

“A beach on the island can hold up to 70 people. But sometimes the number of tourists was well over 1000 on the beach, which was already crowded with food stalls and tour boats. This caused the island to quickly deteriorate.

“If it’s not closed now, we’ll lose Koh Tachai permanently.”

Koh Tachai is part of Thailand’s Similan National Park and its closure is part of a wider plan for resource management in the Andaman Sea.

The island was recently rated by website beachmeter.com as Thailand’s most beautiful island.

Just a short speedboat ride from the Thai mainland, Koh Tachai is renowned for its white sand beaches and crystal-clear waters.