Similan Islands

Marine protected area in Phang Nga Province, southern Thailand

The Similan Islands (หมู่เกาะสิมิลัน, , , Malay: Kepulauan Sembilan) is a continental archipelago in the Andaman Sea off the coast of, and part of, Phang Nga Province in southern Thailand. It is the maritime border between India and Thailand. It was established as Mu Ko Similan National Park in 1982 after a one year assessment by the forestry department.

Access to the Similan Islands is primarily through Tab Lamu Port, located just south of Khao Lak in Phang Nga Province. The park headquarters is situated in Tab Lamu, a small fishing village approximately from Bang La On in Khao Lak. Regular boat services to the islands operate from the middle of October to the middle of May, with trips taking around three hours on standard boats and approximately 70 minutes by speedboat. During the diving season, liveaboard dive boats frequent the Similan Islands. These boats, departing from Tab Lamu, Ko Lanta, Phuket, and Ranong, offer multi day stays in the Similan National Marine Park. The Similan Islands Park has experienced significant visitor traffic, making it one of Thailand's most overcrowded national parks. Data reported by the Department of National Parks (DNP) indicates that since October 2017, the park has received 883,438 visitors. The peak season, from mid October to mid May, typically sees five to six thousand visitors per day. The high visitor numbers have led to environmental degradation, prompting increased regulatory measures. Annually, the park is closed during the rainy season, from 16 May to 15 October. Specifically, the island of Ko Tachai has been indefinitely closed to tourists since 15 October 2016 to facilitate environmental recovery. Following its re opening on 15 October 2018, the park implemented a daily visitor limit of 3,850 to mitigate environmental impact. This measure represents a reduction from the previous average of about 7,000 visitors per day. In 2017, the park attracted approximately 912,000 tourists. The introduction of these restrictions has elicited responses from tour operators, who express concerns over potential job losses. Additionally, as part of the rehabilitation efforts, all overnight accommodations on the islands have been removed.

Within the Similan and Surin National Parks, specific islands, namely Islands 1, 2, and 3, are restricted from public access. This measure is in place to support a turtle hatching protection program and to aid in reef conservation efforts. Notably, Island number 3 is privately owned by a member of the Thai royal family. Although fishing activities are officially prohibited in both Similan and Surin National Parks to protect marine life and habitats, observations suggest that fishing boats frequently operate in and around these parks. Divers in the area often report encountering fishing nets entangled in the reefs and illegal fishing traps. Recent years have seen an increase in the discovery of such illegal fishing equipment, particularly in areas outside the most frequented dive sites. These traps have been found to contain a variety of marine life, including trevallies, batfish, barracuda, golden pilot jacks, and triggerfish. Notably, the regions around Ko Bon and Ko Tachai have been identified as having a higher prevalence of these fishing traps.

The archipelago has been designated an Important Bird Area (IBA) by BirdLife International because it supports a population of Vulnerable pale capped pigeons.