Short version: Mu Ko Similan National Park closes to visitors on May 15, 2026 and stays closed for the entire monsoon season — until mid-October 2026. The 2025–2026 season opened on October 15, 2025, and the final weeks are running now. If the Similans were on your list for this trip, you have about 30 days to get there. Seats on speedboats sell out quickly as the closing date approaches.
After 12 seasons on this route, the pattern repeats every year: the last two weeks of April and the first week of May are the most tightly booked. Last season (May 2025), we had zero seats left for May 10–14 by mid-April.
Key Takeaways
- Closure date: May 15, 2026
- Next opening: approximately mid-October 2026
- Why it closes: southwest monsoon, rough Andaman Sea, coral reef recovery
- Who this affects: anyone planning the Similans between May and October 2026
- What to do now: book a tour for the remaining weeks while seats are available
Primary sources: 5 Star Marine Phuket (January 6, 2026); Thailand Department of National Parks (DNP); TAT News; Thai Meteorological Department — Andaman Sea.
Why Do the Similan Islands Close Every Year?
According to 5 Star Marine Phuket (January 2026) and the Thailand Department of National Parks, Mu Ko Similan National Park closes to visitors on May 15, 2026 for the full southwest monsoon season. The five-month pause protects boats from rough seas, gives coral reefs time to recover, and coincides with sea turtle nesting on the islands.
The Similan archipelago is a protected area within Mu Ko Similan National Park, not a standard beach resort. Thai authorities close it every year for a five-month monsoon break for three reasons.
Navigation safety. From mid-May, the Andaman Sea turns stormy. The southwest monsoon brings tall swells, squalls, and strong currents. Landing on the islands from a speedboat or catamaran is unsafe in those conditions.
Ecosystem recovery. Coral reefs and beaches absorb hundreds of thousands of visitors across a season. Five months without humans give corals and marine life time to recover. This is one reason the underwater world of the Similans is still rated among the best in Southeast Asia.
Sea turtle nesting. The monsoon season coincides with the nesting period of green turtles and hawksbill turtles on the islands — the beaches get complete quiet exactly when they need it.
A practical note: the final working days of the season are unpredictable. In the 2023–2024 season, the park closed two days earlier than announced because of an incoming storm front. If you book a tour for May 13–14, keep a backup day in your holiday schedule.
What Will You See at the Similans Before May 15?
The Similan archipelago is nine islands located 60 km northwest of Phuket, with underwater visibility up to 30 meters in season. Key stops on a day tour: Sail Rock on Island №8, Princess Bay beach on Island №4, and the coral garden off Island №7, considered one of the finest in Southeast Asia.
The main stops that day tours visit:
- Island №8 (Koh Similan) — the iconic Sail Rock boulder and the viewpoint with postcard views over the bay.
- Island №4 (Koh Miang) — the long white Princess Bay beach and a calm snorkeling lagoon.
- Island №7 (Koh Payu) — one of the best snorkeling spots with a coral garden right off the shore.
- Underwater world — visibility up to 30 meters, schools of parrotfish, moray eels, soft corals, occasional mantas and turtles.
In the 2025–2026 season, the park runs in standard mode: daily visitor caps, permit-based landings, lunch served under shade on Island №4.
One detail worth flagging: overnight stays on the islands have been banned since 2019. The Similan tour program is always a single day. If you see an offer for a «two-day tour with an overnight on the island,» it’s either an overnight on the mainland in Khao Lak or a violation of park regulations.
How Can You Visit the Similans in the Final 30 Days?
Tisland.travel (operating in Phuket since 2010) offers three one-day tour formats to the Similans for the remaining weeks of the 2025–2026 season: a classic speedboat, a speedboat with an early departure ahead of the main tourist wave, and a catamaran leaving from Thaplamu Pier for travelers who don’t do well on fast boats.
We run Similan tours daily throughout the season. The three formats differ in pace, comfort, and price — the table below helps you match one to your situation.
| Format | Speed | Comfort in swell | Best for | Book |
|---|---|---|---|---|
| Classic speedboat | High — 3–4 stops per day | Moderate, some bouncing | First trip, want to see the main sites in one day | Similan classic speedboat |
| Similan 7 (early departure) | High, leaves 1–2 hours earlier | Moderate, some bouncing | Crowd-free photos, quiet snorkeling, Island №8 viewpoint in morning light | Similan 7 early tour |
| Catamaran from Thaplamu | Medium, calm pace | High — minimal bouncing, shade, washroom | Families with kids, seasickness, direct departure from the pier | Similan catamaran tour |
1. Classic one-day speedboat tour
The most popular format: pickup from Phuket, transfer to Thaplamu Pier, speedboat crossing, three island stops, lunch, evening return. Good fit if you want to see the highlights without spending multiple days. Full itinerary and dates are in the table above.
The Similan Islands – A Classic Day Trip by Speedboat
2. «Similan 7» — early departure, smaller crowds
Same program, earlier start: you reach the islands ahead of the main tourist wave. The viewpoint on Island №8 and the beaches are effectively empty for the first hour. Good for photography and unhurried snorkeling.
Similan 7 - Excursion to the Similan Islands with an early departure
3. Catamaran from Thaplamu Pier
The catamaran is slower than a speedboat, but the ride is steady, there’s shade, a proper washroom, and you can eat comfortably en route. A format for people who don’t tolerate fast boats well, families with kids, or older travelers. Departure is direct from Thaplamu Pier — no long transfer across Phuket.
Similan Islands by catamaran (start from Taplamu pier)
What Happens to the Similans After May 15?
Starting May 15, 2026, visiting the Similan Islands becomes impossible legally until the next season. The Thailand Department of National Parks typically announces the exact reopening date 1–2 weeks in advance; the reference point is mid-October 2026. Dive centers shift to Phi Phi Islands, Racha, and Koh Khai — but these are not an equivalent substitute in water clarity or reef condition.
After the park closes for the 2026 monsoon, reaching the Similans will be legally impossible — neither on a group excursion nor on a private boat. Dive centers and tour operators shift to alternative Andaman Sea destinations: Phi Phi, Racha, Koh Khai, James Bond Island. These islands stay accessible year-round, but they are not a replacement for the Similans in water clarity or coral condition.
The next opportunity to visit the Similans is the 2026–2027 season, opening approximately in mid-October 2026. The exact date is announced by the DNP usually a couple of weeks before opening — follow TAT News or get in touch with us.
Similan Islands FAQ: Before the Closure
Can you visit the Similan Islands after May 15, 2026?
No. The national park closes fully to visitors until the next season. Any «private» offers after that date are illegal and unsafe: the Thai coast guard turns boats around, and operators face fines and license revocation.
When will the Similans reopen?
Approximately mid-October 2026. The exact opening date for the 2026–2027 season is announced by the Thailand Department of National Parks (DNP) 1–2 weeks before opening.
Speedboat or catamaran — which is better for the Similans?
Speedboat is faster and more dynamic: 3–4 stops in a day, denser itinerary. Catamaran is more comfortable in swell, suitable for families with kids and travelers prone to seasickness. Both formats visit the same islands in the archipelago.
Is it worth booking in the last days of the season?
Yes. By May the sea usually has some chop, but crossings to the Similans run normally through May 14, 2026 inclusive, and weather on the islands is typically still excellent. The main risk is not weather but full boats — demand spikes sharply toward May 15.
Do you pay a separate fee to enter Similan National Park?
No. The national park entrance fee (around 500 baht for foreign visitors) is included in the price of a Tisland tour. No additional on-site payment is required.
What should you bring to the Similans?
A photo ID (park entry is name-based), sunscreen (reef-safe is preferred — standard formulas are prohibited around the reefs), a towel, a change of clothes, cash for souvenirs. Snorkeling gear and lunch are included in the tour price.
What to Do Right Now
If the Similans were on your list for this trip, don’t put it off. Roughly 30 days remain until Mu Ko Similan National Park closes. After May 15, 2026, the next legal opportunity to reach the archipelago comes only in mid-October 2026. In the final weeks of the season, Tisland’s group speedboats and catamarans fill faster than usual — part of the dates is already taken by group bookings, and by May 10–15 only scattered seats remain.
Pick a format: classic speedboat, early departure, or catamaran from Thaplamu. Or browse the full Tisland sea excursion catalog — if the Similans don’t fit your dates, Phi Phi and Racha are available year-round. Message us if you’re unsure which date fits your weather and schedule best — we’ll advise.
After May 15, the next chance comes only in six months.
Sources: 5 Star Marine Phuket — «Similan Islands Will Close May 15th, 2026» (January 2026); Thailand Department of National Parks (DNP) — annual regulation on seasonal closure of Andaman marine parks; TAT News — official announcements from the Tourism Authority of Thailand; Thai Meteorological Department — southwest monsoon forecasts for the Andaman Sea; Mu Ko Similan National Park (Wikipedia) — reference information on the archipelago. All primary source links appear in the Key Takeaways box and inline in the article.
