Top 10 Things to Avoid When Preparing for Your Koh Samui Trip
How well you prepare often decides how relaxed your Koh Samui holiday starts out. Most of the classic mistakes are easy to avoid with a few minutes of research — and some advice that's been circulating online for years is simply out of date by now. We've fully fact-checked our ten most common trip-prep mistakes for 2026.
10. Packing too much, or too heavy
Excess baggage is one of the most expensive annoyances at check-in. The reason: many airlines from Europe allow 25-30kg of checked baggage on the long-haul leg, but the onward flight from Bangkok to Koh Samui usually has a much lower limit. On domestic Thai economy tickets that's typically around 20kg — and on a combination ticket with the same airline, their overall weight limit applies to the whole journey anyway.
Weigh your luggage before you leave so the airport scale doesn't surprise you. The old trick of shifting excess weight into your hand luggage works less and less often in 2026: many gates now weigh carry-on bags too. Pre-booking extra baggage online is almost always cheaper than paying for it at the counter.
9. Not checking your travel documents in time
Your passport needs to be valid for at least 6 months on entry — counted from your arrival date in Thailand, not your departure date — plus have at least one blank page left for the entry stamp. Without that, an airline can turn you away at check-in, or immigration can deny you entry. Check this for yourself and your whole family a few weeks before departure.
There's officially no fine-backed legal duty in Thailand to carry your passport on you at all times — but immigration explicitly recommends carrying either the passport or at least a copy of the photo page with your current entry stamp. Anyone who can't produce any proof of identity during a check risks temporary detention until it's sorted out.
If you lose your passport, contact your embassy in Bangkok immediately. You'll find the key numbers in our Top 10 Phone Numbers for Your Trip to Koh Samui. A useful tip: save scans of your passport, driving licence and insurance documents to the cloud beforehand (email, Dropbox, iCloud), so you can access them from anywhere in an emergency.
8. Packing the wrong things
Koh Samui is tropical, with temperatures around 30°C year-round. You won't need thick jackets, jumpers or multiple pairs of socks day to day — open shoes or flip-flops work almost everywhere. If you do need thin socks at some point (hiking, a cold, or an air-conditioned room), you can buy them locally without any trouble.
One thing we're correcting from the old version of this article: a travel adapter is not unnecessary. Thailand uses plug types A, B, C and O at 220V/50Hz. If you're coming from a country with a different plug type (for example type G in the UK or Ireland), you will need an adapter — many hotels do have combination sockets, but you shouldn't rely on it. A voltage converter, on the other hand, isn't needed: most modern devices run fine on 100-240V.
| Better left at home | Better bought locally |
|---|---|
| Thick jackets, jumpers, multiple pairs of socks | Sunscreen, mosquito repellent (see below), flip-flops |
| Large amounts of cash exchanged at home | A Thai SIM card (airport, phone shops, 7-Eleven) |
| Bulky printed guidebooks | A waterproof phone pouch, rain cover for the wet season |
7. Exchanging money at the wrong time or place
For Thai baht, you'll generally get a better rate exchanging money in Thailand itself than back home. Avoid the counters right in the airport arrivals area — their rates are almost always worse than in town. In Bangkok, two independent exchange chains both trading as "Super Rich" have built a reputation for good rates (orange: SuperRich 1965, and green: SuperRich Thailand); both are usually competitive but change daily, so it's worth comparing the two. After that, a low-fee travel debit card for ATM withdrawals is often cheaper for everyday spending on Koh Samui than repeatedly exchanging cash.
New entry rules since 15 September 2026: nationals of around 60 countries, including most of Europe, can now stay visa-free for only 30 days (previously 60). The stay can be extended once by 30 days in Thailand; anyone planning longer needs a visa. You also have to complete the TDAC digital arrival card online before you travel (no earlier than 3 days before arrival). Rules differ by nationality, so check with the Thai embassy for your passport.
Proof of funds on arrival: immigration officers can ask you to show enough money for your stay. Thai embassies currently state 20,000 THB per person or 40,000 THB per family for visa-free entry, in cash or foreign currency; older figures from the Tourism Authority of Thailand said 10,000 THB. Not every flight gets checked, but it's safest to plan for the higher amount.
6. The wrong mosquito protection, or none at all
Per World Health Organization guidance, sprays containing DEET or icaridin protect reliably — available locally at any pharmacy or 7-Eleven, or ordered before you travel. Mosquitoes are most active in the early morning and at dusk; reapply after swimming or exercise. Dengue fever is a real risk in Thailand, but manageable with the right precautions — for details, the current risk picture and official sources, see our own article Dengue Fever in Thailand: A Risk on Your Trip?
5. Planning too little time per place
A common planning mistake is trying to fit too many destinations into too little time. Thailand has so many facets that rushing rarely pays off — fewer places and more days in each usually means you see more in the end, not less. For Koh Samui itself, 4-5 days is a realistic minimum if you want to fit in beaches, temples, a viewpoint or two, and at least one boat trip (to the Ang Thong Marine Park, for example).
4. Travelling without health insurance
Travel health insurance covers treatment costs in an emergency and, in the worst case, repatriation — Koh Samui has several hospitals with a high standard of care, but treatment without insurance is expensive. Providers range from mainstream national travel insurers to international options aimed at long-term travellers, such as Pacific Cross or SafetyWing; before booking, compare what's covered and whether treatment is billed directly (cashless) or you have to pay upfront and claim it back.
Thailand has been publicly discussing a possible mandatory insurance requirement for arriving tourists since 2026 — as of September 2026 this rule is not yet in force and no start date has been officially confirmed. Regardless, we consider travel health insurance an absolute must for any trip to Thailand.
3. Choosing the wrong way to get there
Bus, overnight train plus ferry, or a direct flight — which suits you best depends on your budget and how much time you have. The direct flight from Bangkok actually takes around 1 hour 15 minutes and lands at one of the most beautiful airports in the world, though it's noticeably pricier than comparable domestic routes because of the operator's monopoly on the island. If your holiday time is limited, the extra cost is almost always worth it. For every option with duration and price range, see our article How Do I Get to Koh Samui?
It's also worth planning your arrival at the airport itself: instead of finding a taxi at the terminal, you can book a private transfer straight to your accommodation in advance.
from 550 THBKoh Samui Airport Transfer Chaweng Arrival & Departure4.94 from 116 reviews
2. Falling for overpriced accommodation
Prices on Koh Samui range from affordable to outrageous. Accommodation that isn't directly on the beach is usually much cheaper than well-known beachfront hotel chains — and villas or holiday homes often offer more space for less money than a branded hotel. Compare several booking sites and date ranges before booking; for a rough overall budget for your trip, including accommodation, food and activities, see How Much Does a Holiday on Koh Samui Cost?
1. Ignoring the weather forecast entirely
Koh Samui has its own distinct microclimate that differs noticeably from Thailand's west coast (Phuket, Krabi) — it's often rainy season there when Samui is at its best, and vice versa. Applying west-coast rules to Koh Samui is an easy way to plan your trip for the wrong time of year. For the full month-by-month breakdown of rainfall and sea temperature, see our in-depth article Koh Samui Weather and the Truth About the Rainy Season.
Frequently asked questions
What should you know before travelling to Koh Samui?
Mainly the points above: a passport valid for at least 6 months, a realistic baggage limit for the onward flight from Bangkok, enough cash for the funds check on entry, travel health insurance, and a look at the weather forecast for your travel dates.
What should you definitely do on Koh Samui?
That depends on your interests — beaches, temples, a boat trip to the Ang Thong Marine Park or to Pig Island (Koh Madsum) are highlights for most visitors. You'll find a full overview in our hub articles on activities and sights on Koh Samui.
When should you not travel to Koh Samui?
There's no truly wrong time to visit, but the rainy season from mid-October to mid-December brings the most rainfall, sometimes in longer spells, and boat trips are occasionally cancelled. See the linked weather article for the exact month-by-month breakdown.
What do I need to know before travelling to Thailand?
Beyond the points in this article: check the visa rules that apply to your nationality well in advance. We've summarised the current rules in Thailand Visa 2026 for Tourists.
For more on planning your trip, see our articles on getting to Koh Samui, the cost of a holiday on Koh Samui, and the Thailand visa in 2026.
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