Similan Islands

"Similan" comes from a Yawi (local Malay) word for "nine"; in Malay it is Kepulauan Sembilan, after the original nine islands, numbered south to north: Ko Hu Yong (1), Ko Payang (2), Ko Payan (3), Ko Miang (4), Ko Ha (5), Ko Payu (6), Ko Hin Pousar (7), Ko Similan (8) and Ko Bangu (9). Island 8 is the largest, and Island 4 hosts the park's island headquarters.

After about a year of assessment by the Royal Forest Department, Mu Ko Similan National Park was declared in 1982. In 1998 Ko Bon (Ko Talu) and Ko Tachai to the north were added, making 11 islands. Ko Tachai lies in Khura Buri district, about 48 km from Island 8; the archipelago lies in Ko Phra Thong subdistrict, Khura Buri.

Island 1, Ko Hu Yong, has the park's longest, widest beach, but landing is banned because sea turtles nest there; Islands 1–3 are closed to protect turtles and reefs, and Wikipedia says Island 3 is owned by a member of the royal family. Since 1995 the navy's Third Area Command has run a royally sponsored turtle conservation centre, incubating eggs on Hu Yong and rearing hatchlings at the Phang Nga naval base. In 2023 staff collected 164 nests and produced over 11,000 hatchlings; about 300 green turtles nest each season, peaking May–October, and hatchlings are raised for 3–6 months before release.

The tsunami of 26 December 2004 caused severe damage. Divers underwater at the time described being swept up by a sudden, violent current.

Corals at Similan and Surin suffered heavy losses twice, in 1998 and 2010, losing about 90%; the 2010 event was linked to a reverse Indian Ocean Dipole. They gradually recovered, and in August 2019 the park announced they had nearly fully recovered.

The Similans have faced more than two bleaching events. Department of Marine and Coastal Resources data cited by Thai PBS records bleaching in Thai waters in 1991, 1995, 1998, 2003, 2005, 2007 and 2010. In 1991 and 1995 about 10–20% of Andaman coral died, but 2010 was the worst, killing about 80–90% in the northern Andaman, including the Similans. Beyond warm water, reefs are also stressed by trampling, boat anchors, fish feeding and trawling.

Ko Tachai once had an 800 m white beach, a campground and a restaurant, but crowds damaged its shallow blue coral through boat anchors and cooking wastewater. The DNP director signed an order on 10 May 2016 closing Ko Tachai "indefinitely" from 15 May 2016 (Wikipedia gives 15 October 2016). Landing and snorkelling are banned, but deep dive sites around the island stay open.

A 2022 survey found Ko Tachai's coral recovering, and the marine park advisory committee discussed reopening. Marine scientist Thon Thamrongnawasawat backed reopening only under strict control. In April 2024 the environment ministry was reported to be preparing to reopen after seven years, but in May 2025 the DNP said it was not ready because the coral had not recovered enough, and it would need at least two more years.

At peak, the Similans drew 6,000–7,000 visitors a day, and about 910,000 in 2017, beyond their carrying capacity. In October 2018 the DNP, working with Kasetsart University, capped daily visits at 3,325 day-trippers and 525 scuba divers and banned overnight stays. Tour operators objected and won an injunction from the Phuket Administrative Court, but in March 2019 the Supreme Administrative Court overturned it, allowing the limits.

Behind the visitor-cap case, Nipon Sommoh sued the DNP and its director-general to revoke two announcements dated 9 October 2018, one capping visitors (3,850 a day in total, 525 divers) and one setting boat fees. The Phuket Administrative Court suspended the cap from 1 January to 31 March 2019, but Supreme Administrative Court Order 78/2562 reversed it, finding the director-general had authority to set conservation measures and citing 2017–2018 visitor numbers averaging 4,512 a day and peaking at 7,302. This was an interim order on the suspension, not a ruling on the merits.

Current rules cap Island 4 at 1,700 visitors a day, Island 8 at 1,625, and divers at 525 across 21 dive sites. No overnight stays are allowed; bungalows and campgrounds have been removed. Visitors may be on the islands only from 08:00 to 16:00, and the sole restaurant, on Ko Miang, opens 08:00–14:00. During the 2020–2021 COVID season there were no foreign visitors at all.

The park has added rules as problems arose: freediving and long fins are banned; liveaboards must anchor farther out and ferry guests by dinghy because anchors had dragged across coral; and giant boat slides were banned after someone broke an arm. In early January 2023 the conservation page "Khaya Morasum" posted photos of short-finned snorkellers standing on coral, and on 4 January 2023 the environment minister posted: "If we can't look after it once it's open, better not to open it." Earlier, on 8 October 2022, minister Varawut Silpa-archa led a team repairing three mooring buoys, including one at the underwater sculpture dive site, and collecting underwater rubbish before the season opened.

The monsoon closure is not only about safety. The 2025 closure notice (16 May–15 October) gave three reasons: letting nature recover, protecting visitors from unstable weather, and reducing disturbance to coral and rare marine life. In the last days before closing, foreign tourists were still queuing for boats to the Similans.

Ko Bon lies about 23 km north of Island 9, known for underwater pinnacles and strong currents suited to experienced divers, with the best chance of manta rays around April–May. Tachai Pinnacle is among the hardest dives. Sea turtles, several shark species and moray eels are common, while whale sharks appear only occasionally around March–April.

On land, the islands are a BirdLife International Important Bird Area for the vulnerable pale-capped pigeon, and are also home to Nicobar pigeons, mangrove monitors, flying foxes and hairy-legged land crabs. Fishing is banned in the park, yet divers still find illegal nets and traps.

The main departure point is Thap Lamu pier, about 20 km south of Khao Lak and home to the park's mainland headquarters, about 65 km from the main islands: around 70 minutes by speedboat or 3 hours by standard boat. Ban Nam Khem pier north of Khao Lak serves Ko Bon and Ko Tachai. Most visitors stay in Khao Lak and go as a day trip.

The 2026–2027 season runs from 15 October 2026 to 15 May 2027. Before opening, a "Save Similan" cleanup was held on Islands 4 and 8, with more than 70 staff stationed at Islands 4 and 8 and the Ko Tachai dive site. Protected Area Management Office 5 reported total revenue of 1,000 million baht across its parks in fiscal 2026, and operators said about 80% of advance bookings were from foreigners.