Park rules
The 3,850 Daily Cap and Similan's Park Rules
Similan limits visitors to 3,850 a day and bans overnight stays, single-use plastics and reef-toxic sunscreen.
Check dates and availability ↗Mu Ko Similan visitor limits and enforced rules
| Rule | Detail | Legal basis / date |
|---|---|---|
| Daily visitor cap | 3,325 day visitors + 525 divers = 3,850 | DNP, upheld by Supreme Administrative Court |
| Overnight stays on the islands | Banned — all bungalows and campsites closed | Announced 2018 |
| Single-use plastics | Banned in all national parks | Royal Gazette 5 Apr 2022, in force 6 Apr 2022 |
| Reef-toxic sunscreen | Four chemicals banned | In force 4 Aug 2021 |
| Maximum fine | Up to 100,000 THB | National Park Act B.E. 2562 (2019) |
| Park hours | 08:00–16:00 | DNP |
Where the 3,850 figure comes from
The cap is not a rule of thumb. Research commissioned by the Department of National Parks, carried out by fisheries researchers at Kasetsart University, assessed carrying capacity and recommended a daily limit of 3,325 day visitors plus 525 divers — 3,850 in total. Before the limit, the park was seeing figures reported at around 7,000 people a day. Tour operators challenged the cap in the courts; the Supreme Administrative Court overturned a lower Phuket ruling and allowed the department to impose it. Divers are counted against their own quota, which is why they pay a separate daily supplement.
What the cap feels like in practice
Nearly four thousand people a day is still a lot for two small beaches, and the cap does not spread arrivals evenly. Most day boats reach the islands within the same two-hour window mid-morning, so Donald Duck Bay and the Sail Rock trail are busiest between roughly ten and one. The park recorded more than 400,000 visitors in a season, around ninety per cent of them foreign. The practical response is not to avoid the islands but to pick an operator whose itinerary runs counter to the crowd, and to do the Sail Rock climb first rather than after lunch.
No hotels, no tents, no exceptions
Until 2018 you could sleep on Koh Miang in one of thirty-five basic bungalows or in one of two campgrounds with around forty tents, together housing up to 190 people a night. The department closed all of it, citing the impossibility of handling sewage and rubbish on a small remote island. There is now no accommodation of any kind on the Similan Islands, and no camping. Anyone offering you an overnight stay on the islands themselves is selling something that does not exist. The only legitimate way to sleep in the archipelago is aboard a liveaboard moored offshore.
Sunscreen and plastic bans carry real penalties
Since 4 August 2021 Thailand has banned sunscreens containing oxybenzone, octinoxate, 4-methylbenzylidene camphor and butylparaben from marine national parks, because these compounds interfere with coral larval development. Separately, a Royal Gazette notification of 5 April 2022 banned single-use plastics from all national parks from the following day, covering thin carrier bags, plastic food containers, cups, straws, cutlery and foam boxes. Both are enforced under the National Park Act B.E. 2562 (2019), with a maximum fine of 100,000 baht. Buy a reef-safe sunscreen before you travel and pack a reusable bottle.
The rest of the rulebook
The standard marine park prohibitions apply and rangers do enforce them: do not feed the fish, do not touch, break or collect coral, shells or marine life, and do not stand on reef. Boats must use designated mooring buoys rather than anchoring, and unapproved vessels cannot enter park waters at all — which is why every legitimate trip runs on a licensed operator's boat. The park operates 08:00 to 16:00, so day trips are built around a hard afternoon departure. Operators also expect you to carry insurance covering snorkelling or diving.