Thailand has two distinct island coasts—the Andaman Sea (west) and the Gulf of Thailand (east). They are not connected by short ferries; you fly or bus between coasts. We hop islands on long weekends too; this guide helps you pick a coast, time the weather, and link trips without wasting days in transit.

Andaman Sea (west) — dramatic karsts and diving

Clear water, limestone cliffs, and famous beaches. Best base airports: Phuket, Krabi, and Trang.

• Phuket: Largest island hub; ferries to Phi Phi, Racha, and day trips to Phang Nga Bay.
• Krabi / Ao Nang / Railay: Gateway to Hong Island, Four Islands tour, and ferries toward Lanta.
• Koh Phi Phi: Iconic bays; book ferries from Phuket or Krabi; very busy in high season—consider Phi Phi Don vs day trips to Phi Phi Leh.
• Koh Lanta: Relaxed, family-friendly; long beaches; slower pace than Phuket.
• Koh Lipe: Far south near Malaysia; stunning water; multi-leg journey from mainland—worth it for a finale stop.

Typical hop: Phuket → Phi Phi (2–3 nights) → Krabi/Railay (2–3 nights). Allow buffer days for sea conditions.

Gulf of Thailand (east) — calmer gulf, full moon fame

Warm gulf water, different monsoon timing from the Andaman. Airports: Koh Samui, Surat Thani (ferries to islands), Chumphon (for Koh Tao).

• Koh Samui: Upscale resorts, easy airport; ferries to Koh Phangan and Koh Tao.
• Koh Phangan: Beaches and parties; also quiet north coast stays.
• Koh Tao: Diving certifications and snorkel trips; smaller island vibe.
• Koh Chang (near Trat, eastern Gulf): Jungle interior, waterfalls; closer to Bangkok by road—no need to fly south.

Typical hop: Fly to Samui → Phangan (2 nights) → Tao (3 nights for diving). Catamaran companies sell multi-island tickets—compare luggage limits.

Ferries and booking

• Major operators (e.g. Lomprayah, Seatran, Phi Phi Cruiser, Andaman Wave) sell online; hotel desks add markup but help with pickups.
• High-speed catamarans are faster; slow ferries are cheaper and steadier if you get seasick.
• Monsoon months can cancel boats—build one spare day before flights home.
• Protect bags from spray on open decks; dry bags are cheap at pier shops.

Seasons (simplified)

• Andaman: Dry-ish peak roughly November–April; heavier rain and some pier closures May–October (west coast monsoon).
• Gulf: Often reversed—Samui / Tao / Phangan can be wetter October–December while Andaman is sunny; check month-by-month if you only have one week.
• Shoulder months (May, June, October) can offer deals and fewer crowds with acceptable weather luck.

See our climate and seasons article for regional detail.