Things to Do in Koh Tao in May

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Stay in Koh Tao in May

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Opens Trip.com on Fri 7 May to Sun 9 May 2027; change the dates there.

May is when the rain returns to Koh Tao. The island logs about 189mm (7.4 in) across 22 rainy days, more than double April's total, and most of it arrives as short, heavy afternoon bursts rather than all-day grey. Days sit at 29.2°C (85°F) and nights barely fall to 27.0°C (81°F), so the air stays thick and warm around the clock and the shallows off Sairee Beach feel like bathwater.

The payoff for divers is underwater. May is the tail end of the spring plankton season at the offshore pinnacles, where visibility can still run 20-30m (65-100ft) before the murkier months that follow, and dive schools in Mae Haad and Chalok Baan Kao are noticeably quieter after the April Songkran rush, meaning smaller groups on the boats.

May is low season on Koh Tao, and you'll notice it. Some bungalows around Tanote Bay and Aow Leuk cut staff or close for repairs, and late in the month the southwest monsoon starts pushing swell into the Gulf of Thailand. Come in May for the diving and the empty beaches. If you want dry skies you can count on, February or March is the better pick.

Why visit in May

Beachfront rooms on Sairee Beach that sell out in January can usually be booked a day or two ahead in May.
Open Water courses in Mae Haad and Chalok Baan Kao often run with 2-4 students per instructor, down from the full boats of the December-April high season.
Snorkelling at Tanote Bay and Hin Wong Bay on the east coast tends to stay calm until the southwest monsoon strengthens in June.
Boats to Koh Nang Yuan carry noticeably fewer day-trippers from Koh Samui than in the Easter weeks.

Worth knowing

Afternoon thunderstorms, most often between 2pm and 6pm, can cancel the second dive trip of the day and keep longtail taxis on the beach.
At midday the heat index sits around 34-35°C (93-95°F), so the climb from Chalok Baan Kao to the southern viewpoints is a slog after 10am.
Whale sharks never show on a schedule. Some Mays go by with only a handful of confirmed encounters at the island's dive sites.

Best for

Think twice if

Weather measured 29° / 27°C 189mm rain · 22 rainy days · 78% humidity rains perceptibly ~3.2h/day · 63% of mornings dry

Crowds low

Pack Quick-dry shorts, loose linen or synthetic shirts, sandals that grip on wet concrete in Mae Haad, and a 3mm shorty or rash guard for 30°C (86°F) water.

May is when Koh Tao swings from the dry Gulf season into the southwest monsoon. Mornings over Sairee Beach are usually bright, cloud builds by about 1pm, and on most days a heavy squall rolls through in the afternoon before it clears by sunset. Nights stay sticky and hardly cool at all. October and November are far wetter at 275mm and 336mm, so May is wet by dry-season standards, not monsoon ones.

Seasonal caution

The southwest monsoon usually strengthens over the last 10 days of May, and the high-speed catamaran from Chumphon, which takes about 1.5-2 hours, can get rough enough that operators sometimes cancel sailings when swells reach 2-3m (6.5-10ft).
Lightning storms over the Gulf of Thailand are common on May afternoons, and dive boats head back to Mae Haad pier early when strikes get close. Swimmers at Freedom Beach and Shark Bay should get out of the water at the first thunder.

Year-round climate

Averages from the last 5 years.

Monthly climate averages for Koh Tao
Month	Avg high (°C)	Avg low (°C)	Rainfall (mm)
Jan	27	25	20
Feb	27	25	76
Mar	28	26	33
Apr	29	27	80
May	29	27	189
Jun	29	27	120
Jul	29	26	172
Aug	28	26	145
Sep	28	26	192
Oct	28	25	275
Nov	28	25	336
Dec	27	25	135

Holidays and festivals in May

Public holidays

National Labour Day(วันแรงงานแห่งชาติ)1 May 2027
Coronation Day(วันฉัตรมงคล)4 May 2027
Visakha Bucha Day(วันวิสาขบูชา)20 May 2027

Best things to do in May

Whale shark dives at Chumphon Pinnacle and Sail Rock

diving

Chumphon Pinnacle is a granite pinnacle about 11km (7 miles) northwest of Koh Tao, and Sail Rock sits roughly halfway to Koh Phangan. Both drop to about 30m (100ft) and draw big schools of barracuda and trevally.

May closes the spring window when plankton brings whale sharks to the Gulf pinnacles, and the boats carry fewer divers than they do in March.

Booking tipBook the Sail Rock day trip 2-3 days ahead, because in low season many Mae Haad operators need 8-10 divers before they'll run it.

Open Water or Advanced course in small groups

diving

The standard PADI or SSI course takes 3-4 days, starting in the pool or at shallow bays like Japanese Gardens and moving on to sites such as Twins and White Rock.

Class sizes drop after the Songkran peak, so instructors spend more time with each student on skills.

Booking tipAsk for a morning-first schedule so any session lost to a storm can move to the next day.

East-coast snorkelling at Tanote Bay and Hin Wong Bay

snorkelling

Tanote Bay has a boulder reef about 50m (165ft) from shore with parrotfish and blacktip reef sharks, while Hin Wong Bay is rockier and has no sand beach at all.

The east coast faces away from the southwest winds, so it tends to stay clearer than the west-side bays as May goes on.

Booking tipTake a pickup taxi from Mae Haad and agree the fare before you leave, because the road to Hin Wong is steep.

Early longtail to Koh Nang Yuan

island trip

Koh Nang Yuan is three small islands joined by a sandbar, about 15 minutes by longtail from Sairee, and it charges a landing fee and bans plastic bottles.

May mornings are the driest part of the day, and an 8am boat gets you there hours before the afternoon storms and the Samui speedboats.

Booking tipArrange the longtail with a Sairee beach driver the evening before, and set the pickup time in writing.

Sunrise hike to John-Suwan Viewpoint

hiking

The trail starts above Chalok Baan Kao and climbs about 20 minutes over boulders to a view of both Shark Bay and Chalok Baan Kao bay.

At 6am the temperature is still bearable, and the rocks are dry before any afternoon rain makes them slick.

Booking tipThere's a small entry fee at the trailhead, so bring small notes.

What to eat in May

In season: fruit

Durian (Monthong and Chanee)
Durian from orchards in Chumphon and Surat Thani provinces hits its peak in May and June, and ferries bring it to fruit stalls around Mae Haad pier.
Mangosteen
Mangosteen season starts in May on the Gulf mainland, and by mid-month the purple husks usually show up at fruit carts along the Sairee Village path.
Rambutan
Rambutan from Surat Thani province starts arriving in late May, and the main harvest continues into July and August.

Street food peaks

Khao niao mamuang (mango sticky rice)
The Nam Dok Mai mango season runs March to May and ends this month, so stalls in Mae Haad may already be using fruit from further afield by late May.

Regular events in May

Labour DayFree

A national holiday that gives many Thai workers a long weekend, and some of them take the ferry from Chumphon to Koh Tao, so the islanders' beaches get a little busier.

May 1

Coronation DayFree

A public holiday marking the coronation of King Vajiralongkorn: government offices and banks close, but dive shops and bars stay open.

May 4

Royal Ploughing CeremonyFree

A Brahmin rice-planting ritual held at Sanam Luang in Bangkok to open the growing season, though on Koh Tao it mostly means government offices close for the day.

Mid-May, date set by royal astrologers

Visakha Bucha DayFree

Thailand's holiest Buddhist day marks the birth, enlightenment and death of the Buddha, and temples hold candlelit wian tian processions at dusk, walking three times around the ordination hall.

Full moon of the sixth lunar month, usually mid-to-late May

Full Moon Party at Haad Rin, Koh Phangan

The monthly beach party at Haad Rin on neighboring Koh Phangan, with Lomprayah and Seatran running boats there from Mae Haad pier.

On or near the May full moon

Best places this May

Tanote Bay
beach
A small east-coast cove with a jumping rock about 5m (16ft) high, sheltered from the prevailing wind this month.
Tanote
Koh Nang Yuan
island
The viewpoint on the southern island is about a 15-minute climb and looks out over the sandbar and Sairee to the southeast.
Off Sairee
John-Suwan Viewpoint
viewpoint
The best sunrise spot on the island's southern tip, with Shark Bay on one side and Chalok Baan Kao on the other.
Chalok Baan Kao
Freedom Beach
beach
A short cove at the end of the Chalok Baan Kao headland where shallow coral starts right off the sand, making it a good morning swim before the clouds build.
Chalok Baan Kao
Hin Wong Bay
snorkel spot
A rocky east-coast inlet with some of the island's clearest near-shore water, though the last stretch of road there is unpaved.
Hin Wong
Sairee Beach
beach
The 1.7km (1.1 mile) west-coast strip where May sunsets often light up the clouds of a passing storm.
Sairee
Aow Leuk
beach
A deep, sandy east-side bay with a gentle slope, good for first-time snorkelers on calm mornings.
Aow Leuk

Your packing checklist

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Packable rain shellAfternoon squalls on Koh Tao tend to pass quickly, and a light shell beats an umbrella on a longtail or in a pickup taxi. Shop
20-liter dry bagLongtail rides to Koh Nang Yuan and Mango Bay get soaked by spray and rain, so your phone and passport need a sealed bag. Shop
Reef-safe mineral sunscreenThe UV index stays near 12 in May even under thin cloud, and Koh Nang Yuan asks visitors to keep chemical sunscreens off its reef. Shop
Seasickness tabletsTake one 30 minutes before a late-May ferry or a dive boat to Sail Rock, when the swell is at its roughest of the spring. Shop
DEET insect repellentDengue cases in Thailand usually rise from May as rain leaves standing water, and Aedes mosquitoes bite during the day. Shop
Swimmer's ear dropsSeveral dives a day in warm, humid conditions make ear infections one of the most common reasons Open Water students lose a day. Shop
HeadlampStorms sometimes cause short power cuts in Sairee and Chalok Baan Kao, and the back lanes have almost no street lighting. Shop

Insider tips

Book the morning boat. Most Mae Haad schools run a 7am and a 12pm trip, and in May the afternoon one is the one that gets cut.
Check the Chumphon sailing the evening before you leave in late May, and if the forecast looks bad, the Samui route via Koh Phangan is often calmer.
Low-season walk-in rates at Sairee bungalows often beat online prices, and many owners give a further discount for 7 nights.
Stock up on beer the night before Visakha Bucha, as 7-Eleven tills across Thailand block alcohol sales for the whole holiday.
The concrete roads to Tanote Bay and Aow Leuk are very steep and turn slippery after rain, so a pickup taxi from Mae Haad is the safer call over a rented scooter.

Avoid these mistakes

People book the ferry out on the last day of a 4-day Open Water course, which means one storm cancellation can push the final dives into departure day, and the 18-24 hour no-fly rule still applies to onward flights from Chumphon or Koh Samui.
A lot of visitors plan Koh Nang Yuan for the afternoon, which is when the storms and the Samui day-trip speedboats both show up at about the same time.
Counting on clear water at Sairee in the last week of May is a gamble: southwest chop often stirs up the west side, and the east coast is the better bet then.

Practical tips for May

Book ferries 1-2 days ahead at the Lomprayah or Seatran offices at Mae Haad pier, and in late May, go for morning sailings because seas are usually calmer before the afternoon wind picks up. Many low-season bungalows in Tanote Bay and Aow Leuk take bookings direct, so message them before you arrive by taxi. Cover shoulders and knees at temple ceremonies on Buddhist holidays. Make sure your travel insurance names scuba diving to 30m (100ft): the island has a recompression chamber near Mae Haad, but serious cases go by boat to Koh Samui. Some Sairee restaurants shorten their hours in May, and kitchens often close by 9pm midweek.

FAQ

Is May a good time to visit Koh Tao?

It's a fair month, ranking 7th of the 12 for a general trip, though it's much better for divers than for beach loungers. Small dive groups and low-season rooms are the reward; planning around a storm most afternoons is the trade-off.

What is the weather like in Koh Tao in May?

Hot and humid, with showers most days. Mornings are usually clear, cloud builds by lunch, and a squall lasting about 30-60 minutes tends to hit in mid-afternoon. Nights stay nearly as warm as the days, so a fan alone often isn't enough to sleep well.

Is Koh Tao crowded in May?

No. Midweek, Sairee Beach can feel half empty, and while visitors from Bangkok and Hua Hin fill some rooms over the Labour Day and Coronation Day long weekends, dive boats in Mae Haad rarely sail full.

Can you see whale sharks off Koh Tao in May?

Possibly. Sightings at the offshore pinnacles tend to taper off during May, and some weeks pass without any. Sail Rock usually gives better odds than the sites closer in, so it's worth at least one day trip.

Is Koh Tao welcoming for LGBTQ+ travelers?

Yes. Koh Tao scores 8.5/10 for LGBTQ+ friendliness (sourced from TTDI's editorial rubric). The dive-school crowd in Sairee and Mae Haad is international and relaxed, and couples rarely draw a second look on the island.