First trip to Thailand: the planning mistakes that cost the most

Pick your month deliberately, stay longer in fewer places, and sort out three things before you fly: your stay length, your health cover and how you will get cash.

Who it’s for: anyone planning a first trip of one to four weeks. Who can skip it: repeat visitors who already have a SIM, a card strategy and a favourite base. The visa, medication and licence sections still apply to you.

Choose the season, not the “best time”

Generic “best time to visit” lists ignore what you want. Decide what you are buying: dry weather, low prices or fewer people. You cannot have all three. Thailand’s meteorological scheme has three seasons.

Four things the table hides:

• Smog. In the dry season, crop burning, traffic and still air push PM2.5 to unhealthy levels across the north and parts of the centre, and Chiang Mai is often among the worst. If you are booking Bangkok or the north in the dry season, check the daily PM2.5 reading (air4thai.pcd.go.th) before you commit and avoid non-refundable bookings.
• Heat. From March to May, plan temples and markets for the morning, retreat indoors after lunch, and drink water before you are thirsty. Heat exhaustion is common among visitors who pack a full day into the sun.
• Songkran. The Thai New Year runs from 13 to 15 April, with water fights in every city. It is a highlight, and also one of the most crowded and expensive weeks of the year. Book early, and expect to get soaked.
• The Gulf islands run on a different calendar. On Koh Samui and Koh Phangan, October to December is the wettest stretch, with November the peak, so the “dry season” advice for the rest of the country does not apply there.

Early rainy season, roughly June and July, is the best compromise: a shower most afternoons, clear mornings, cheap rooms and thin crowds. The worst of the rain falls later, from about September into October.

Know how long you can stay

As of October 2026, most Western passports get 30 days visa-free, for tourism only. Confirm yours on the entry rules board. If you want longer, you have two clean routes:

• Extend once, by up to 30 days, at an immigration office; check the current fee there. Take your passport, a copy of its photo and visa pages, a passport photo and the money. Approval is at the officer’s discretion, so don’t rely on it for a booked flight.
• Apply for a tourist visa before you fly, which gives a longer first stay.

Check the visa guide for your passport, and file the free arrival card within three days before you land. Your passport needs at least six months’ validity.

Ask your accommodation for its TM30 receipt. Immigration offices can ask for proof that your host reported your address when you apply for an extension, so it is worth requesting up front. The TM30 guide explains it.

Do not overstay. The fine is charged per day, up to a cap if you surrender at the border before leaving; check the current figure with immigration.

An overstay of more than 90 days brings a re-entry ban of at least a year, and more than a year at least three; people caught by immigration before they surrender face longer bans. Check the current schedule with the Immigration Bureau. Immigration offices are closed on weekends and public holidays, so book your extension appointment days before the deadline, not on it.

Fewer places, more nights

A common itinerary mistake is a stop-start trip of two nights per place. Every move costs a morning: check-out, transit, then waiting for a room to be ready. Plan at least three nights in each larger destination.

If you want a structure, anchor each stop with one planned activity: a walking or cycling tour, a cooking or Muay Thai class, or an animal sanctuary that does not offer rides or close contact. Two or three days of that beats five stops on a map.

Booking tours. Reviews are your protection against the weak or scam operators in the tour trade. Book through a platform that shows a public price and a large number of recent reviews, read the lowest ratings first and compare across more than one platform. A listing is not a guarantee, so confirm the pickup details and the cancellation terms before you pay.

Health: vaccines, medicines, insurance

Vaccines. The US Centers for Disease Control recommends hepatitis A and typhoid vaccination for most travellers to Thailand, and hepatitis B for unvaccinated adults under 60.

Japanese encephalitis is advised for stays of about a month or more, or for rural trips with camping or unscreened lodging, but not for short city trips. Malaria risk is limited to certain areas, so ask the clinic whether your route touches any.

Your own risk depends on where you go, the season and what you do. See a travel clinic four to six weeks before you leave.

Medicines. Many drugs that need a prescription at home are sold over the counter in Thai pharmacies, so a refill is usually easy.

For your own medication:

• Keep it in the original labelled packaging, with a doctor’s letter, and check how many days’ supply the rules allow (30 days is the usual limit to look for).
• Some medicines need a permit. Some narcotic and psychotropic medicines need a Thai FDA permit, applied for at least 15 days ahead. Look your medicine up on the Thai FDA’s online portal for travellers before you fly.

Insurance. Thailand’s private hospitals are excellent and priced accordingly, so an accident or admission without cover is expensive. Buy a policy before you leave, read the exclusions (some leave out motorbike injuries, adventure activities and pre-existing conditions) and check that it covers medical evacuation. The healthcare guide shows what treatment costs.

Getting around

Match the mode to your time:

Compare fares on a flight search site and set a price alert from a few months out.

For trains, use the State Railway of Thailand’s own booking channels or a station counter, and check how far ahead tickets go on sale. Within cities, use a ride app such as Grab or Bolt rather than flagging a street taxi, because the fare is agreed up front and the ride is tracked.

Drivers sometimes cancel and ask you to pay cash. Decline and rebook.

Where to sleep

You have three choices. Match one to your length of stay.

Read recent Google reviews as well as the booking site’s. If you do book a condo unit, choose a host with a long review history, read the reviews for building complaints, and photograph the unit on arrival, because “different unit from the listing” is a known complaint.

Where to stay in Bangkok covers the neighbourhoods.

Budget

Costs vary by region and season, and they climb from November to February.

Check current costs on the cost of living page.

Money

Cash. Skip exchanging at home: rates there are poor, and Thai booths offer better ones. Dedicated exchange booths usually beat bank counters and hotel desks.

Bring your passport, and bring clean, undamaged large notes, because booths turn away torn or worn ones.

ATMs. Thai banks charge foreign cards a fee on every withdrawal; the machine shows it before you confirm. Your own bank may add its own charge. So:

• Withdraw larger amounts less often. Machines cap a single withdrawal, so check the limit on screen.
• Choose a card that refunds ATM fees, and tell your bank you are travelling.
• Decline “convert to your home currency”. It uses the machine’s own rate, which is almost always worse than your bank’s.
• Take your card. Thai machines often give cash first and return the card afterwards, the reverse of many Western ones, and people walk away without it. Bring a second card as a backup.

Cards. Credit cards are widely accepted in hotels, restaurants, shops and on ride apps, usually at good exchange rates. Foreign-card fees apply, and a cash advance on a credit card is costly, so pay with the card and do not draw cash on it.

Declaring cash. Large amounts of cash must be declared at the border; the money guide has the limits.

Staying connected

You have three options for a phone:

1. Roaming from your home carrier. Fine for a short trip if the plan is reasonable. Check the daily price first.
2. An eSIM bought before you fly. Active when you land. Your phone must be unlocked and eSIM-capable, and it costs more than a local SIM.
3. A Thai prepaid SIM. Airport counters sell tourist packages for a few days to a month. Mall shops of the main carriers and 7-Eleven stores also sell local plans. Bring your passport, because registration requires it.

If you swap your home SIM for a Thai one, you lose your home number, and with it any text-message codes for your bank. Move your accounts to an authenticator app before you leave. A calling app that gives you a home-country number is a useful backup.

Packing

Pack light. Thailand sells nearly everything, and low-cost airlines charge for checked bags, sometimes nearly as much as a short flight. See what to pack for the specifics.

If you plan to drive or rent a scooter, bring an international driving permit along with your home licence. Most guidance, including insurers’, is to carry an IDP that covers motorbikes plus your home licence. Rental shops will often hand over a bike without checking, but police can fine you, and travel insurance may refuse a claim if you crash without the right licence.

The driving licence guide has the detail.

Think twice about learning to ride here. Thailand’s road death rate is among the highest in Asia, and most victims are on motorbikes. If you have never ridden, a Thai side road is a poor classroom.

Download Google Maps with an offline pack, plus Grab and Bolt for rides, before you land. Some apps need a Thai phone number to register, so install those after you have a local SIM. The full list is in Thailand apps you need before you arrive.

Next, read your first hour in Bangkok: the arrival card, immigration, cash and the ride into town, in the order you meet them.