Ferries and speedboats are how most visitors reach the Thai islands. A handful of operators run the main routes, timetables bend to the weather, and the most useful thing you can do is spend two minutes checking the boat, the sea and the life jackets before you step on board.
Thailand has two island coasts with opposite weather. On the Andaman side (Phuket, Krabi, Phi Phi, Koh Lanta, Koh Lipe) the rough months are roughly May to October. On the Gulf side, the UK Foreign Office says the rainy season on Koh Samui and in the southeast usually runs from November to March. That single fact explains most cancellations, most seasick crossings and most of the advice on this page.
Booking itself is the easy part. Our guide to 12Go.asia and combined bus-and-boat tickets covers how to book online and compare operators. This page is about the boats: who runs which routes, what the terms really say, and how to judge whether a crossing is safe.
Thai ferries at a glance
- Gulf operators
- Lomprayah (catamarans and bus-boat tickets), Seatran (car ferries from Donsak), Songserm (express boats)
- Andaman operators
- Tigerline and partners (Phuket to Koh Lipe and Langkawi), Bundhaya Speedboat (Pak Bara and Langkawi to Koh Lipe), among others
- Rough season
- Andaman coast about May–October; Gulf islands about November–March (FCDO)
- Life jackets
- Marine Department rule reported by TAT: all passengers wear them at all times on board
- Check-in
- Lomprayah asks passengers to arrive 60 minutes before departure
- Emergency
- 1669 ambulance, 191 police, 1155 Tourist Police
Who runs the boats on the Gulf of Thailand
The Gulf islands of Koh Samui, Koh Phangan and Koh Tao are served from Chumphon and from the Surat Thani area. Lomprayah is the name most visitors meet first. It runs high-speed catamarans between the three islands and sells through-tickets from its Bangkok office at Pinklao, with a bus to the coast and a boat onward. It also connects Surat Thani Airport with the islands and runs a Koh Tao to Chumphon Airport service with a transfer.
Seatran runs the car-ferry corridor from Donsak, near Surat Thani, to Koh Samui and Koh Phangan. If you are driving a rental car across, this is the type of boat you need, and Seatran asks vehicles to arrive at least 45 minutes before departure. Songserm runs express boats linking Samui, Phangan and Koh Tao and sells e-tickets by card on its own site.
For route-by-route detail, see our guides to getting to Koh Samui and getting to Koh Tao. If you plan to move between all three islands, the Gulf island-hopping route puts the legs in order.
Who runs the boats on the Andaman Sea
The Andaman coast has more operators and more speedboats. Tigerline describes a network running from Phuket through Phi Phi, Koh Yao Noi and Yao Yai, Koh Lanta and the Trang islands down to Koh Lipe, with a link to Langkawi in Malaysia. It says its boats run daily between about 07:00 and 18:30, with schedules adjusted by route, season and weather. Bundhaya Speedboat sells Pak Bara to Koh Lipe, Phuket to Phi Phi and Langkawi to Koh Lipe.
On Koh Lipe, boats land at Pattaya Beach. Our older guide on how to travel to Koh Lipe covers the piers on the mainland. For the busiest Andaman crossing, see Phuket and Krabi to Phi Phi, and for a longer trip the Andaman island-hopping route.
Shorter hops close to the mainland work differently. Boats to Koh Larn leave from Pattaya (see our Koh Larn guide), and Koh Chang is reached by car ferry from Trat province; we cover that crossing in Bangkok to Koh Chang. Bangkok's river boats are a separate system again, explained in our page on the Chao Phraya Express Boat.
Speedboat, catamaran or slow ferry
| Type | Good for | Watch out for |
|---|---|---|
| Large car ferry | Vehicles, heavy luggage, people who get seasick | Slowest option; long walk from pier to town on some islands |
| High-speed catamaran | Most island-to-island trips on the Gulf; indoor seating | Can be cancelled or rough when the wind picks up |
| Speedboat | Short hops, small islands without big piers | Hard jolts in waves; little space for bags; exposed to spray |
| Longtail boat | Beach transfers, short trips to nearby bays | Open boat; only suitable in calm water |
Songserm's own advice on speedboats is blunt: people prone to motion sickness should take precautions beforehand, and anyone with back problems should consider another option, because speedboats jolt. Pack light and keep valuables in a waterproof bag.
Safety checks before you board
The UK FCDO says passenger boats between the mainland and the islands have sunk or collided, with deaths including British nationals, and names three usual causes: overloading, poor maintenance and rough seas, especially in the monsoon. All three are things you can look at from the pier.
- Count the seats and the people. If passengers are standing in the aisles or sitting on the roof, the boat is overloaded. Wait for the next one.
- Find the life jackets before departure. TAT reported in 2016 that Marine Department rules require all boat passengers to wear a life jacket at all times on board. Check there is one for every passenger, including child sizes.
- Look at the sea, not the sky. White caps outside the harbour mean a rough crossing in a small boat even on a sunny day.
- Watch the flags. TAT says port officials use red and green flag signals to warn boat operators about the weather. A red flag at the pier is a reason to ask questions.
- Note who is in charge. On a reputable boat the crew gives a short safety briefing and knows where the exits and life rafts are.
A cheaper speedboat in a building swell is the classic mistake. If the big catamarans are delayed for weather, a small boat that is "still going" is not a bargain. Accept the delay and keep a buffer day before any international flight.
What the ticket terms usually say
Read the operator's terms before you pay, because they shape what happens when things go wrong. Lomprayah's terms (updated May 2026) are a useful example of how the bigger companies work:
- Arrive at the Lomprayah office at least 60 minutes before departure to confirm the trip.
- One large bag up to 20 kg travels free; over 20 kg costs an extra 200 baht. Small bags and handbags are free. Surfboards and folding bicycles cost extra.
- Tickets are non-refundable. You can change the date once without a fee if you tell the company at least two days ahead, with the new date within 90 days.
- Timetables can change without notice because of weather, and the company does not cover missed flights or trains.
- Children under 2 travel free; ages 2 to 11 pay half price.
Other operators have their own rules, so check the terms on the company's own site. The point that applies everywhere is the last one in the list: a ferry company will not pay for your missed flight. Check what your travel insurance says about weather delays.
Monsoon cancellations and how to plan around them
The FCDO advises following the Thai Meteorological Department for weather warnings and notes that weather patterns have become less predictable. In practice, operators cancel or merge departures when the sea is too rough, sometimes on the morning of travel. Smaller speedboat routes are usually the first to stop.
Some island services are seasonal by design. The Similan Islands are only open from 15 October to 15 May (see our Similan Islands guide), and many boats to the smaller Andaman islands thin out in the wet months. Our guide to the best time for the Thai islands compares the two coasts month by month.
Book the first boat of the day in the rough season. If the first departure is cancelled, you still have later boats, or a day in hand, before your onward connection.
Frequently asked questions
Do I need to book Thai ferries in advance?
For the main Gulf routes and popular Andaman routes in high season, booking a day or more ahead is sensible, and through-tickets from Bangkok must be booked in advance. Outside the peak months you can usually buy at the pier, but the cheapest connecting buses may be full.
Are ferries in Thailand safe?
Thai authorities have tightened boat rules over the years, but the UK FCDO notes that boats have sunk or collided because of overloading, poor maintenance and rough monsoon seas. Avoid overloaded boats, wear the life jacket and accept weather delays rather than switching to a smaller boat.
Do ferries to the Thai islands run in the rainy season?
Most main routes run year-round, but departures are cancelled or delayed when the sea is rough, and some small-island routes are seasonal. The Andaman coast is roughest from about May to October; the Gulf islands get most rain from about November to March.
How much luggage can I take on a Thai ferry?
It depends on the operator. Lomprayah allows one large bag up to 20 kg free and charges 200 baht for heavier bags, with extra fees for surfboards and bicycles. Speedboats have far less space, so a soft bag is easier than a large hard suitcase.
Sources
- UK FCDO – Thailand travel advice: Safety and security (sea travel, rainy season) (checked October 2026)
- Tourism Authority of Thailand – Marine safety measures and regulations in Thailand (June 2016) (checked October 2026)
- Lomprayah – Terms of Service (checked October 2026)
- Lomprayah – Routes and services (checked October 2026)
- Seatran Ferry – Donsak car ferry (checked October 2026)
- Songserm – Express boats and speedboat advice (checked October 2026)
- Tigerline – Andaman ferry and speedboat network (checked October 2026)
- Bundhaya Speedboat – Routes (checked October 2026)