Thailand in May: what to expect

May is the handover month. The southwest monsoon reaches the Andaman coast first, so Phuket, Krabi, Koh Lanta and Khao Lak get the earliest and heaviest rain, plus swell that puts red flags on the beaches. The Gulf islands — Koh Samui, Koh Phangan, Koh Tao — run on the opposite rhythm and stay largely dry and calm through September, which makes them the pick this month.

Bangkok and central Thailand are hot and sticky, with the first downpours of the season usually arriving in the afternoon or evening and clearing within an hour or two. The north (Chiang Mai, Chiang Rai, Pai) is hot rather than wet, and the burning-season haze of February to April has usually washed out by now — check AQI before booking if air quality matters to you.

Temperatures sit in a narrow band nationwide: 33–35 °C by day, 25–27 °C at night, with the north a degree or two cooler after dark. It is not the 38 °C of April, but humidity is higher, so the heat feels heavier. Plan outdoor sightseeing before 11am and after 4pm.

May is one of the two quietest months of the Thai year, sitting between the Songkran rush in April and the European summer holidays in July. Beaches, temples and domestic flights are noticeably emptier, and you can often book a room a few days ahead rather than weeks.

Prices follow the crowds. Low-season rates apply on both coasts, with the deepest discounts on the Andaman side — the trade-off is that some boats, dive shops and beach restaurants there scale back or close for the monsoon. Gulf island resorts stay open and busy enough to keep standards up, but still charge less than in July and August.

Book transport early only around the Visakha Bucha full moon and the long weekend that sometimes forms around it; otherwise May is a month where you can improvise.

The month's main fixed point is Visakha Bucha, which falls on the full moon of the sixth lunar month — late May or early June, so check the exact date for your year. It marks the Buddha's birth, enlightenment and passing. Temples fill in the evening with candlelit processions, and alcohol sales are banned nationwide for the full day, including in bars and supermarkets.

The Royal Ploughing Ceremony, an ancient Brahmin rite marking the start of the rice-growing season, is held at Sanam Luang in Bangkok, usually in May. Dates are set by the royal calendar, so confirm locally.

Beyond that, May is a month of ordinary Thai life: temple fairs, local fairs and the start of the rice season in the villages. It is a good month for markets and cooking classes because there are no crowds to fight.

Go east and south into the Gulf. Koh Samui, Koh Phangan and Koh Tao are in their dry season, with calm water for snorkelling, diving and boat trips. Koh Samet, closer to Bangkok, also works for a short break.

Bangkok is fine if you accept the heat: temples and museums in the morning, malls, markets and rooftop bars once the afternoon storm passes. Kanchanaburi and Ayutthaya are day-trip options, though both are exposed and hot at midday.

In the north, Chiang Mai and Chiang Rai are green and quiet, with low hotel rates and waterfalls at their best. Air quality is usually better than in March and April, but confirm AQI before you commit if you are sensitive.

Skip the Andaman coast unless you are going for the mainland towns rather than the sea. Phuket and Krabi still function, but expect rough water, red flags, cancelled boat trips and the Similan and Surin islands closed.

Pack for heat and sudden water. Light, quick-drying clothes in breathable fabrics beat cotton; a compact umbrella or light rain shell earns its place more than a heavy raincoat. Bring reef-safe sunscreen, insect repellent for the evenings, and a dry bag for boat days and storms.

For temples, cover shoulders and knees — a light scarf or sarong handles both. If you plan to dive or snorkel on the Gulf side, your own mask is worth the space. A small power bank keeps your phone alive on long travel days.

April is hotter and busier, with Songkran filling transport nationwide. June is similar to May but wetter on the Andaman side and slightly busier on the Gulf islands as European holidays begin. July brings the first real price rise on Samui, Phangan and Tao.

If your dates are flexible and you want dry weather everywhere, aim for November to February instead — but expect peak-season prices and crowds.

Go if you want the Gulf islands, cheap rooms and quiet temples, and you do not mind heat and an afternoon soaking. Skip it if your plan is Phuket, Krabi or a Similan liveaboard — the sea is rough and the marine parks are shut. The decision hinges on which coast you choose, not on the month itself.