Thai Ferries and Speedboats — Two Coasts, Two Monsoon Seasons, Safety, Seasickness, and Building In a Buffer Day
Thailand's two coasts have rough seas at different times of year. Which islands to visit when, which boat types are safer in swell, why services get cancelled, and how not to miss your flight home.
Island trips in Thailand involve a variable that roads do not: the sea. Boats are cancelled for swell, some islands are unreachable for months, and most boating accidents happen when operators push out in bad weather. This guide collects what to know before buying any boat ticket.
Two coasts, two monsoons
| Coast | Main islands | Rough season (avoid) | Best months |
|---|---|---|---|
| Andaman (west) | Phuket, Phi Phi, Lanta, Lipe, Similan | Roughly May–October; some marine parks close | November–April |
| Gulf of Thailand (east of the peninsula) | Samui, Phangan, Tao | Roughly October–December: heavy rain and swell | January–September |
| Eastern seaboard | Koh Chang, Samet, Kood, Mak | Roughly May–October: rain, moderate swell | November–April |
The useful part of this table is that when one coast is bad, the other is usually good. Mid-year the Andaman is rough but Koh Tao and Koh Phangan are fine. If your dates are fixed, choose the island to suit the season rather than forcing an island into the wrong month.
Boat types
- Large ferries (slow boats): big, stable, carry vehicles, slower, safest in swell; best for seasick-prone passengers and heavy luggage.
- Catamarans and mid-size fast boats: quicker than ferries and still tolerable in moderate seas; used on the Samui–Phangan–Tao run and main Andaman routes.
- Speedboats: fastest, roughest, open or under canvas; tiring and riskier in swell; fine for short hops on calm days.
- Longtails: used to reach beaches larger boats cannot; very short trips, no roof, luggage can get wet.
Signs not to board that boat
- Passengers crammed in with people standing on deck.
- Not enough life jackets visible for the number aboard.
- Other operators have cancelled for weather but this boat is still going.
- A very old boat whose engine stalls repeatedly before departure.
Taking the next boat or staying one more night is always cheaper than the risk.
Seasickness
- Sit low and midships, where the motion is least, not at the bow or stern.
- Look at the horizon, not your phone.
- Take motion-sickness tablets at least half an hour before boarding; taking them once you feel ill is too late.
- Both an empty stomach and a full one make it worse; eat lightly beforehand.
- Choose a slow ferry over a speedboat if you know you suffer, even if it costs time.
Planning the trip home around your flight
- Do not fly out on the same day you leave the island in the rainy season; return to the mainland the night before, especially from islands with only a few boats a day.
- If you must fly the same day, take the first boat and a late flight.
- Combined boat + bus + flight tickets from a single seller sometimes include rebooking if the boat is late; ask about the terms before buying.
- Keep the boat company's number and, in monsoon season, call in the morning to confirm the day's departures before checking out.
Summary
Choose the island for the season before choosing the date, take the bigger boat when there is swell or heavy luggage, refuse boats that look unsafe even at the cost of time, and always build in a night on the mainland before a flight in the rainy season.