- ✓May is the start of the green (rainy) season — the peak heat breaks, the landscape turns lush, and the rain can be brief or prolonged.
- ✓May can bring lower rates and fewer visitors in some destinations as weather patterns shift, but holidays and local demand still affect prices.
- ✓The coast logic tilts: the Andaman starts to get wetter and rougher as its green season begins, while the Gulf islands (Samui, Phangan, Tao) are still in their good more-settled-weather tendency — so May favours the Gulf.
- ✓Inland, the early rains green everything up beautifully — Khao Sok's rainforest, the northern hills and the central plains all look their lushest, and the smoke season is over.
- ✓Best for value travellers, Gulf-island and green-season lovers, and flexible itineraries that can dodge a shower or duck inland.
May weather, region by region
May is the turn of the year, when the punishing heat of April gives way to the green season. The first proper rains arrive, usually as a dramatic afternoon or evening downpour that clears as fast as it comes rather than a day-long grey-out — so May rarely 'rains out' a trip; it punctuates it. The reward is a cooler, fresher feel than April and a landscape that turns vivid green almost overnight.
Bangkok and the central plains stay warm and humid with building afternoon showers, but mornings are often bright and the heat is more bearable than at April's peak — good for early sightseeing and food-focused days. The North is past its smoke season at last: the burning has stopped, the rains have cleared the air, and the hills are lush and green again, making May a quietly excellent and cheap month for Chiang Mai if you don't mind the odd shower.
Inland nature is a May highlight. Khao Sok's rainforest and Cheow Lan Lake are at their most lush and atmospheric, waterfalls run full, and the parks come alive — a strong reason to build a green, jungle-and-lake stop into a May route. On the coasts, the picture splits, which is the key planning fact this month.
The coast call — favour the Gulf in May
May is the month the coast logic clearly tips. The Andaman (Phuket, Krabi, Phi Phi, Lanta) is entering its green season — the southwest monsoon brings more rain, rougher seas and the occasional paused boat trip, so while it's far from a washout (and prices are tempting), it's no longer the reliable beach bet it was in March. The famous beaches can be moody, and some island day trips become weather-dependent.
The Gulf islands, by contrast, are still in their good window. Koh Samui, Koh Phangan and Koh Tao are often more settled from around January to September, though conditions vary, with their heaviest rain saved for much later in the year, so May is a strong, lower-priced month to be on the Gulf side — calmer seas than the Andaman, reliable diving on Koh Tao, and the value of low-season rates. If your May trip is built around beaches and islands, the Gulf is the smarter coast.
The Andaman and Gulf often differ in May, with the Gulf sometimes more settled as the Andaman becomes wetter. Neither offers reliable sun as a guarantee. Keep island-hopping within one coast and confirm sea and ferry conditions for the exact dates.
What to do — and how to plan — in May
May rewards a flexible, value-minded trip. With the heat broken and prices low, it's a fine month for Bangkok food crawls and markets, a green-season North without the crowds or smoke, a Gulf-island beach base, and an inland nature stop at Khao Sok or the parks. Build the day around bright mornings, with the afternoon downpour as a built-in rest, a long lunch or a spa hour — plan loosely enough to wait out a shower rather than fighting it, and May travels beautifully.
Avoid over-committing to fixed Andaman boat days. The Gulf can be more settled in May, but it is not guaranteed; compare live forecasts and marine warnings. Some destinations have lower demand or rates, though both vary by place and date. Pack a light rain layer, keep an indoor alternative and verify ferry status before locking in an island.
Sources and official planning resources
Thailand in May · at a glanceMonth FC
- Season
- Start of the green/rainy season — heat breaks, lush landscape, afternoon downpours
- Coast timing
- Andaman getting wetter & rougher (green season); Gulf still in its good window — favour the Gulf
- Crowds & price
- Low season begins — sharply lower prices and fewer crowds; the value window
- Best for
- Value travellers, Gulf-island and rainforest lovers, flexible itineraries
- Verify event dates
- Check current Andaman sea & ferry conditions — green-season status shifts year to year
