Koh Tao to Krabi

Lomprayah runs the whole trip on one ticket, three times a day from its pier at Mae Haad. The 07:05 speedboat reaches its Krabi office at 13:00 for ฿1,400, the 09:30 catamaran at 15:30 for ฿1,300, and the 11:00 Direct speedboat at 16:00 for ฿1,600. All three call at Phangan and Samui on the way to Donsak, where a van takes over for the drive across. The booking sites sell the two speedboats under the name Lomlahkkhirin, which is the same service, and on the dates I checked 12Go didn't list them at all, so buy those two from Lomprayah if you can't find them.

The 09:30 is the one I'd book. It's the cheapest of the three, and for ฿150 more the same ticket ends at your hotel in Krabi Town at 15:30 or in Ao Nang at 16:30, which saves a taxi from the office. Getting to Mae Haad by 09:00 is easy from Sairee, about ฿100 a person in a shared songthaew.

Lomprayah's office is in Krabi Town, so the base fare suits you only if you're staying there. For Ao Nang, the ฿1,450 hotel ticket is the simple one, and agencies sell the 09:30 boat with their own vans to Ao Nang at about 15:50 to 16:30 for about ฿1,350–1,420, some ending at the McDonald's on the beach road rather than your door. Boonsiri's 08:00 reaches Ao Nang at 15:30 for ฿1,300, though the booking sites list it later in the morning, so check the time on your ticket.

Railay has no road, so a Railay ticket ends with a boat. Lomprayah's goes there at 14:30 on the 07:05 for ฿1,800, at 18:00 on the 09:30 for ฿1,700 and at 18:00 on the 11:00 for ฿2,000, and Boonsiri's reaches Railay East at 16:30 for ฿1,700. Arriving at 18:00 means the last boat of the day, so I'd take the 07:05 for Railay, or a ticket to Ao Nang and the ฿100 longtail across, 10 to 15 minutes.

If you'd like a slower morning, Koh Tao Booking Center's 11:00 reaches Krabi Bus Terminal at about 15:30 and Ao Nang at about 16:00 for about ฿1,780–1,880, and Songserm's 11:30 speedboat and van reaches the bus terminal at about 17:30 and Ao Nang at about 18:30 for about ฿1,600–1,750. Songserm's is the last departure that reaches Krabi the same day. The bus terminal is north of Krabi Town, so from there it's a taxi or songthaew to your hotel.

The cheapest way is the night boat. It leaves Mae Haad at 21:00 with mattresses on an open deck, reaches Surat Thani early in the morning, and a van takes you on to Ao Nang at about 07:00 to 09:00, Krabi Bus Terminal at about 08:00 to 08:45, and Railay by about 09:30 to 10:00, for about ฿850–1,500 on one ticket. One version ends at Krabi airport at about 09:00 for about ฿1,320. It saves a night's room and you arrive with the day ahead of you, though you'll have slept on a boat. Our Surat Thani to Koh Tao guide has more on the night boat.

The Gulf's rough season is October to December, with November the wettest month, and that's when the boats from Koh Tao are most likely to be rough or canceled. Krabi's rainy months run the other way, roughly May to October, so the crossing is calmest from about February to April, when both coasts are at their best. In the Gulf monsoon I'd leave a spare day in Krabi before any flight home.

Going east, Lomprayah leaves its Krabi office at 08:00, 09:30, 11:30 and 13:00, and both Lomprayah and Boonsiri pick up in Ao Nang. Our Krabi to Koh Tao guide has every departure and the night-boat vans.