The park reopened on 15 October after five months shut. The ticket, the sunscreen law and the choice of island all matter more than the choice of boat.
More than 400,000 people visited the Similan Islands last season, and over 90% of them came from abroad. Tourism there brought in more than 215 million baht (about US$6.4 million or £4.8 million), up from 197 million the year before, according to Thailand’s natural resources office (the report is in Thai). Then it shut for five months. It reopened on Thursday 15 October and stays open until 15 May 2027, and Mu Ko Surin, the park further north, opened the same day. Those numbers are the reason to read the rules before you book a boat. The Similans are a handful of small granite islands in the Andaman Sea, and how people behave on them decides whether they cope.
What the 400,000 figure does and does not tell you
Spread across a season of 213 days, 400,000 visitors comes to about 1,900 a day. If that sounds manageable, remember how few places a day boat can land. The department set a daily cap of 3,850 visitors, 525 of these reserved for scuba visitors, when it reopened the park in October 2021. I could not find a newer figure. If that cap still applies, last season’s 400,000 visitors were about half of what the park could have taken, since 3,850 a day over a full season comes to roughly 820,000. But the average hides the busy days. Visitors do not arrive evenly, and I would guess the weeks around Christmas and New Year run far above 1,900 a day. A cap only matters on those days.
Last season averaged about 1,900 visitors a day, which is a lot of boats for a few beaches.
The closure is the other half of the argument. The park’s head says the marine ecosystem needs time to recover and that visitor numbers should be limited, but the same report gives no limit and no measure of reef health. It counts visitors and baht. I do not doubt that five months without boats helps, because closed seasons are a standard tool in marine parks. I would still like to see a published figure for what the rest achieves, and a cap that is written down and enforced, before I call the Similans a managed success. Revenue rising by about 18 million baht in a year points the other way. We covered the 2024 reopening when the questions were about dates. This year they are about numbers.
There is a further reason to hold the visitor count loosely. In March 2025 the Nation reported that the department had moved the park’s head to an inactive post while a committee investigated claims that foreign visitors were being under-registered in the e-ticket system. A task force had counted about 50 passengers on each of 15 boats landing at Islands 4 and 8 in four hours, against about five registered per boat. The claims were not proven in that report, and I found no published result. If the count was ever low, the real pressure on the islands is higher than the headline figure.
Getting in: the ticket, the fee and the sunscreen rule
Foreign adults pay 500 baht to enter (about US$15 or £11) and children aged 3 to 14 pay 250 baht, the same rates the Nation reported for the park in 2025 and the ones operators are quoting for 2026-27. Thai nationals pay 100 and 50 baht. Ask any operator whether the park fee is in the price, because some boats include it and some collect it on the day. The Nation also reported that Similan was the first Thai park to run on e-tickets only, bought in advance with your name and nationality recorded. Operators selling this season say the ticket must be issued before 08:00 on the day of travel, through the department’s QueQ app or its e-ticket portal, and that entry is logged by name, so carry your passport. If you book a day trip, the operator handles all of this. If you go independently, register the evening before. I could not find a 2026 notice on the department’s own pages, so confirm the process with the park office before you rely on any of it. The number is on the department’s park page: +66 7 645 3272. Bring cash for anything on the islands, because card payments are not accepted there.
The sunscreen rule is the one most visitors will break without knowing. The department told every marine park in October 2025 to enforce the ban on four ingredients: oxybenzone, octinoxate, 4-methylbenzylidene camphor and butylparaben. The fine is up to 100,000 baht (about US$2,980 or £2,220). “Reef safe” on a bottle is marketing, not a legal standard, and the ban names four chemicals, so read the ingredient list rather than the front label. Mineral sunscreens and a rash vest cover most of the problem. The same notice asks visitors to stay at least two metres from coral and to keep their hands off it, and rangers fine for touching turtles and shells too. Nobody sleeps on the islands any more: the department ended overnight stays in 2018, so your day ends when the boat leaves, which is 16:00 at the Similans and 16:30 at Surin.
Which islands you can land on, and when to go
The Similans are numbered from south to north, one to nine, with Ko Bon and Ko Tachai as ten and eleven. Day trips normally land on two of them. Island 8, Ko Similan, is the largest and has the Sail Rock viewpoint. Island 4, Ko Miang, is where the park headquarters sits and where most boats stop for lunch and a swim. Island 7 is for snorkelling and scuba only, with no beach landing. Islands 1 to 3 are closed to the public to protect turtle nesting, and Ko Tachai has been closed since October 2016. If a package promises a landing on any of those, ask what you are really paying for. Surin follows the same fees and a similar pattern, with a Moken community living on one of its islands, and operators sell two-day trips there.
Island 8 is one of two Similan islands where day-trip operators land visitors.
Weather is the gamble. Operators warn that the swell is typically stronger in October, and the park can close early if the sea turns before mid-May. One operator rates November as the calmest month, and I would take that as a judgement, not a forecast. Book a boat whose operator lets you move the date for free, and consider a catamaran over a speedboat in the opening weeks if rough water bothers you. Early departures and catamarans sell out first. If you have flexibility, my bet is that a weekday before Christmas will give you more room on Islands 4 and 8 than the weeks after it, and the cheapest way to take pressure off the reef is to pick the day nobody else wants.
The Similans earn their reputation, and the 400,000 people who went last season were not wrong to want to. The reef does not care about the revenue figure, though, and neither does the cap if nobody enforces it. No single visitor can fix that, but you can choose the smaller boat, the quieter day, a sunscreen that passes the ingredient list and an operator who is straight with you about the ticket. That is a small amount of homework for islands that are open for only seven months a year.
Further Reading
- Maya Bay Shuts Its Doors Again: What This Means for Your Thailand Holiday Plans
- Thailand Is Freezing Its Coral Reefs. Here’s Why That Should Matter to Every Diver in Southeast Asia.
- Sustainable Island Tourism in Southeast Asia: A Guide to Eco-Resorts and Responsible Travel
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