The currency of Thailand is the baht, denoted by the symbol "฿" (ISO code: THB), written in Thai as บาท or บ. Wikivoyage uses "baht" in its articles. It is divided into 100 satang (สตางค์). There are six coins and six notes:
The most useful bills tend to be 20s and 100s, as many small shops and stalls don't carry much change. Taxi drivers also like to pull the "no change" trick; if caught, hop into the nearest convenience store and make a small purchase. Beware of 1,000 baht notes, as counterfeits are not uncommon: feel the embossing, look for the watermark and tilt to see colour-changing ink to make sure the note is real.
They are everywhere, and international withdrawals are not a problem, besides the fee. When using a debit card, an ATM will typically provide a much better exchange rate than a money exchange counter, and this is especially the case if you have a card that does not charge a transaction fee for overseas withdrawals (becoming common in countries such as Australia). ATMs are available at Bangkok's Suvarnabhumi airport (BKK) after collecting your bag and clearing customs, and while it is advisable to arrive with a small amount of baht if possible, you may obtain cash from an ATM after landing as well. There's a 220 baht surcharge (up from 150 when it was introduced in 2009-10, then 200 baht) for using foreign cards in most ATMs, you'll be notified about this fee in any ATM which charges it, so you always have an option to cancel. AEON  [dead link], which used not to charge any fee until 2013, still charges 150 baht though - but it's ATMs are few and far between even in Bangkok, and none at the islands besides Ko Samui and Phuket. Most ATMs (including AEON) have a limit of 20 notes, that is 20,000 baht; Bangkok Bank typically dispenses 25 notes at once, and a few other banks including Citibank (but only in Bangkok), Krungsri, TMB and CIMB may dispense 30 notes - which makes them even slightly better than AEON, but only in case you do need 30,000 baht ($900) at once.
More important thing to watch for is that some ATMs (Krungsri, SCB and a few others are known for that) will offer you to exchange your money to Baht for you, charging your card in USD or even your local currency. What you will get if you agree is a very lousy rate (-5% if not more from the mid-market level), so always refuse and choose to be charged in Thai Baht only, not USD or your own currency.
Very remote areas (including smaller islands) do not have banks or ATMs, so cash is essential.
If you wish to avoid high ATM fees by bringing in funds as cash, bring US dollars, they can often be exchanged at competitive rates
One notable money exchanger is SuperRich, with dozens of branches in Bangkok including at Silom, Ratchadamri, Khao San Road and Chatuchak. No fees are charged and the exchange rate, especially for USD, is typically comparable to the Visa/Mastercard's (even before you consider ATM and your local bank fees), with a very small (down to less than 10 satang in the main office) buy/sell spread. They exchange many other currencies, both Western and major regional ones, and the rates are very good too. Their success caused a host of competitors to emerge, some of these closely imitating SuperRich, including in the major cities outside of Bangkok. Their rates are generally good too.
The banks also do offer reasonable rates, though normally not as good as the exchangers mentioned before. In Suvarnabhumi airport, however, all the banks have notoriously bad rates, making you to lose up to 1,5 baht (4-5%) per USD if you exchange there. But there are several money exchangers (including SuperRich) at the basement floor on the way to the Airport Rail Link station, just to the left from the machines selling ARL tokens. Their rates are not much different from those in the city offices.
For a comparison of all the bank's exchange rate check out DaytoDayData or Thailand Exchanges, also available as an app. To identify a good money exchanger, take the difference between the sell and buy rate, divide it by two and then again divide it buy the sell rate, e.g. 42-38/2/42 ~ 5%. This is the percentage of fee you basically pay for the exchange. It can be as low as 0.2-0.5% in the exchange services mentioned before, and thus probably better than withdrawing money from the card, depending on the conditions of your home bank.
Many hotels and guesthouses will change money for guests, but hefty commissions and poor rates may apply. US dollars in small bills (US$1, 5, and 20) are invaluable for onward travel to neighbouring countries other than Malaysia, but are only useful in Thailand for exceptional purchases (e.g., paying visa fees for Cambodia).
Another way to avoid the ATM fee (especially handy for those on extended stays) is to withdraw money via the bank counter, the phrase universally understood in Thai banks is "cash advance". Beware though that most of the card issuers (i.e. your home bank) do charge significantly more for this operation than for ATM withdrawal, even including some cards that are free to withdraw in ATMs - research thoroughly in advance and choose the right card, or you may end up paying to your own bank even more than 220 baht you would have paid to the Thai bank in an ATM! Note also that not every bank, and not even every branch of the same bank offers this service to the foreigners - the best bet is a bigger branch of a major bank, and Bangkok Bank seems to be the most reliable in offering this service, including some of their "Exchange" booths. You'll need your passport to withdraw the money over the counter, and, of course, the bank's operating hours apply (many, but by no way all, branches are also closed on weekends and public holidays).
Cards are widely accepted in the tourist industry such as in restaurants, shopping malls and shops catering to tourists. Fraud is regrettably common though, so use them sparingly and tell your bank in advance, so your card doesn't get locked down because you are using it. Some businesses add a surcharge (usually 2-3%) if you're paying by credit card; in this case, it can turn out cheaper to pay them in cash.
Foreign visitors (with a few exceptions) have the benefit to receive a 7% VAT refund on luxury goods purchased from shops that participate in the 'VAT Refund for Tourists' scheme. When you see a 'VAT Refund for Tourists' sign, you can receive a 7% refund of the VAT levied on goods at the shop. However, certain conditions apply, and you won't be able to claim your refund until you depart Thailand from an international airport.
The goods must be purchased from participating shops that display a "VAT Refund For Tourists" sign. You may not claim VAT refund for services or goods that you use or "consume" while in Thailand; such as hotel or restaurant expenses. On any one day, the goods purchased from any one individual participating shop must be at least 2,000 baht including VAT. When you purchase the goods, ask the sales assistant to complete a VAT refund form, known as the P.P.10, and attach the original tax/sales invoices to that form. Each P.P.10 must show a value of 2,000 baht or more. You will need to show your passport to the sales assistant when you purchase the goods, to allow her to fill in the above mentioned form. When you exit the country, the goods must be inspected prior to check in and your completed P.P. 10's stamped. Since you must give away the original receipts it is a good idea to take photos or make copies in case you need to prove the value of your purchases to customs officers when going home.
Tipping is not common in Thailand and the Thais themselves don't do it. Thais do round up (or down) the taxi fare to get it to an amount that is easier to pay for (such as from 59 or 61 to 60 baht). Sometimes they also leave the change in restaurants, but even this is a rare occurrence.
You don't have to feel odd if you don't tip at all, as that's what the locals do, but the presence of many foreign visitors have changed some expectations. Tipping is now common in many high-end hotels and tourist restaurants. Don't go overboard when tipping — never give more than 50 baht. In some tourist places, especially along Khao San Road, there are even restaurants hinting for a tip. This is not common (and even rude) in Thai culture, so you can easily ignore it.
Do not tip when a customer service charge is applied, as this is supposed to be the tip, applied only in luxury restaurants and hotels.
Thailand is not as cheap as it used to be, with Bangkok being named the second most expensive city in SE Asia behind Singapore. However, budget travellers who are careful with what they spend will still find that 1,000 baht will get a backpacker a dorm bed or cheap room, three square meals a day and leave enough for transport, sightseeing, and even partying. Doubling that budget will let you stay in decent hotels, and if you're willing to fork out 5,000 baht per day or more you can live like a king. Bangkok requires a more generous budget than upcountry destinations, but also offers by far the most competitive prices for shoppers who shop around. The most popular tourism islands such as Phuket and Ko Samui tend to have higher prices in general. It is common for tourists to be charged several times the actual price in tourist areas of other places as well. If you want to have an idea what the real Thai prices are, consider visiting malls like Big C, Tesco, or Carrefour where locals and expats routinely shop. Those are available in major cities (in Bangkok, there are dozens of them) and on larger islands such as Phuket or Ko Samui. Tax hikes have made alcohol clearly more expensive than in some neighbouring countries.
Thailand is a shopper's paradise and many visitors to Bangkok in particular end up spending much of their time in the countless markets and malls. Particularly good buys are clothing, both cheap locally produced street wear and fancy Thai silk, and all sorts of handicrafts. Electronics and computer gear are also widely available, but prices are slightly higher than in Singapore, Hong Kong, Philippines, and Kuala Lumpur. A good strategy for shopping, is to first go around doing window shopping for a couple of days, don't commit yourself to purchase anything until you have seen enough to be able to make sensible judgements. The last thing you want is to impulsively buy something today and two days later see the same or similar item selling at a much reduced price elsewhere. Most shopping centers in Bangkok have sales often, but even better is to go a bit out the big city into a place like Future Park for example. At the Mo Chit minibus rank next to the public park ask for "Future Park" minibus. Go early, the trip costs 35Baht, takes about half an hour and you get a chance to mix with the real Thais going about their daily lives. Once at Future Park shopping complex, its vast multilevel shopping areas go on and on (opens at 10:00, closes at 21:00) and it caters for everyone and everything, cheap and upmarket, from motor vehicles and home appliances, to clothing and furniture, Thai therapy and restaurants. You can spend the day hunting for special deals and shopping with many sales on offer with prices catering for local customers, department stores like Robinson are extensive and a bargain hunters paradise. If you get hungry or thirsty, there's plenty of varied restaurants on offer and also a large supermarket within, with a help yourself fresh salads and other foods bar selling food by weight. The main Zpell entrance facing the elevated freeway is by the minibus rank and once inside there's an information island desk with English speaking staff at hand, while you can always download a translator app to help you just in case. On returning to central Bangkok, go back to the main minibus rank and ask for the "Mo Chit" vehicle, alternatively, return by taxi cab to central Bangkok (100-120 baht), the better option, if you find yourself carrying lots of shopping.
A Thai speciality is the night markets found in almost every town, the largest and best-known of which are in Bangkok and the Night Bazaar in Chiang Mai. Here a variety of vendors from designers to handicraft sellers have stalls selling goods which cannot normally be found in malls and day markets. Most night markets also have large open air food courts attached.
You can also find marvellously tacky modern clothing accessories. Witness pink sandals with clear plastic platform heels filled with fake flowers. Night markets along the main roads and Bangkok's Mahboonkrong (MBK) Mall, near the Siam Skytrain stop, are particularly good sources. Not to be left out is what is often touted as the world's biggest weekend bazaar - The Chatuchak Weekend Market or known to locals simply as "JJ" Market. Chatuchak sells a myriad of products ranging from clothes to antiques, covers over 35 acres (1.1 km²) and is growing by the day!
Haggling is the norm and often market and road-side vendors will try to charge you as much as they think you can afford to pay. It's not uncommon to buy something, walk outside, and find somebody who bought the same item for half or one third what you paid (or even less). Try to figure out the item's rough value first. Adjacent stalls, government-run fixed price shops and even hotel gift shops are a good starting point. You'll find that prices drop drastically when the seller realizes you have some idea of what it costs.