Southern Thailand's islands sit in two different sea systems — the Andaman (Phuket, Phi Phi, Krabi) and the Gulf (Samui, Phangan, Tao). Weather, ferry reliability, and sensible routes differ between them. A plan that works in January can be dangerous or simply cancelled in September.
Andaman versus Gulf: why it matters
The southwest monsoon hits the Andaman coast hardest roughly May–October. Seas can be rough, speedboat links pause, and some beaches lose swim access. The Gulf side is not immune — Samui and surrounds have their own wet season patterns — but operators sometimes run different calendars.
Do not assume one national weather forecast covers both coasts.
Popular routes
Phuket → Phi Phi → Krabi (Andaman classic)
Allow 7–10 days minimum. Phuket (HKT airport) is the usual entry point. Ferries connect Phuket Town or Rassada Pier to Phi Phi; onward boats reach Krabi (Ao Nang / Railay area).
Timing: November–April is the usual dry window on the Andaman. Shoulder months can still work — check daily sea state.
Visa note: Count your stamp from entry. Island hopping does not reset immigration; build a buffer before your permitted stay ends.
Koh Samui → Koh Phangan → Koh Tao (Gulf triangle)
Samui (USM airport or Surat Thani + ferry) is the hub. Phangan is a short ferry; Tao is north for diving courses.
Timing: Many travellers use the Gulf mid-year when Andaman seas are rough — but still verify ferry status. Full-moon event weekends on Phangan affect accommodation and boat crowding.
Krabi-only loop (Railay, Hong islands, Lanta)
Krabi Town or Ao Nang as base; day trips to Railay and island tours. Koh Lanta suits slower travel and longer stays if ferries are running.
Best time to visit
| Coast | Typical dry window | Caution months |
|---|---|---|
| Andaman (Phuket, Phi Phi, Krabi) | Nov–Apr | May–Oct rough seas |
| Gulf (Samui, Phangan, Tao) | Often Dec–Apr best | Oct–Dec can be wet; check locally |
Holiday weeks (Thai New Year in April, Western Christmas–New Year) spike prices and sell out ferries — book ahead.
Getting around
Scheduled ferries connect major islands with published timetables. Buy from official counters or reputable agents — not ad-hoc street touts at the pier.
Long-tail boats work for short hops in calm weather. Agree price and destination before boarding.
Speedboats save time when the operator will run and the sea allows. Life jackets and weather checks are non-negotiable in monsoon season.
Domestic flights between Phuket, Krabi (via road), and Samui save days when seas are closed — compare total cost including airport transfers.
Before each leg
- Passport dry bag and photocopy of visa stamp page
- Confirmed ferry time and pier name (many towns have multiple piers)
- Cash for remote islands with limited card acceptance
- Buffer days before visa expiry — islands are not border runs
Costs and budgeting
Island transport adds up: ferries, national park fees, taxi from pier to hotel, and speedboat tours. Budget more than mainland city rates for the same comfort tier.
Estimate transfers from HKT, USM, or BKK to your first hotel before you lock an itinerary.
Safety and visa compliance
Rough seas cause cancellations — build flex days into the itinerary. Immigration cares about the stamp date, not your hotel checkout. If you need more time, extend or exit before overstaying.
See Phuket city hub and the tourist visa guide.
