Thailand's islands: Andaman or Gulf, and when?

The Andaman: the dramatic coast

The Andaman coast means limestone cliffs rising straight from the sea, mangrove channels and bays best seen from a longtail boat or a kayak. In Phang Nga Bay the karsts stand like stage scenery, on Koh Yao Noi life still turns around fishing and rubber, and further south are Koh Mook, Koh Kradan and Koh Lipe, with clear water and reefs just off the beach.

The best time here is usually November to April: calmer seas, clearer skies and regular boats between the islands. From May to October the south-west monsoon arrives – rain often comes in short, heavy bursts, but the sea can be rough, some boat routes between the smaller islands thin out or stop, and some places to stay on the more remote islands close.

The Gulf: gentler and calmer

The Gulf islands are different: fewer dramatic cliffs, more coconut palms, soft hills and long beaches. Koh Samui is the largest and easiest, with an airport and a wide choice of stays, though its quieter shores feel very different from the busy ones. Koh Phangan is known to many for its parties, but its northern and eastern bays are another world. Koh Tao is known for diving and snorkelling, and the Ang Thong marine park for limestone islets on a day trip.

In the Gulf the wettest period is usually late October to December, and the driest from January to August. So in July and August, when Lithuanian schools are on holiday and the Andaman side is in its rainy season, the Gulf is often the better choice. Families might also look at quiet mainland shores such as Khanom.

By month, roughly

• November: the Andaman season begins while the Gulf is still wet – head west.
• December to March: the Andaman is usually at its best; the Gulf is lovely too from January. Also the busiest, most sought-after time.
• April: both coasts are usually fine, but very hot.
• May to September: the Gulf is generally the better choice; the Andaman is green and quiet, but the sea can be rough.
• October: a changeover month on both sides – build in flexibility.

What about both coasts in one trip?

Possible, but rarely necessary. Getting from one coast to the other means crossing the mainland or flying via Bangkok – close to a day's travel. It makes most sense around April, when both sides are usually dry, or on a longer trip where one coast is for active days and the other for a quiet finish. On a two-week trip that also includes the north and Bangkok, we'd usually choose one sea and give it all the remaining time.

Which one for you

If you're dreaming of dramatic scenery, kayaks among the karsts and hopping between islands by boat, and you're travelling between November and April – the Andaman. If you're travelling with children in summer and want long, calm beaches and simpler logistics – the Gulf. For a honeymoon both work, just at different times.

One more piece of advice for either coast: two islands with four or five nights each beat five with one night apiece. Every move means a transfer, a boat and another check-in, and island rhythm only shows itself when you stop hurrying.

In Thailand the sun is almost always shining somewhere – it's a matter of knowing which way to look.

Tell us when you can travel and how you picture your days by the sea – active or idle, just the two of you or with children. Together we'll choose the coast and the islands that will be at their best then.