Money

The currency of Thailand is the baht (THB, ฿), written in Thai as บาท or บ. There are six coins and six notes:
* 25 and 50 satang (cent, copper colour) coins - nearly worthless and only readily accepted (and handed out) by buses, supermarkets and 7-11s
* 1, 5 (silver colour), 2 (gold) and 10 baht (silver/gold) coins
* 20 (green), 50 (blue), 100 (red), 500 (purple) and 1000 (grey-brown) baht 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 1000-baht notes, as counterfeits are not uncommon: feel the embossing, look for the watermark and tilt to see color-changing ink [18] to make sure the note is real.

ATMs can be found in all cities and large towns, and international withdrawals are not a problem. 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 want to obtain most of your cash from an ATM after landing.
More remote areas (including smaller islands) don't have banks or ATMs, so cash or traveller's checks are essential. Many hotels and guest houses will change money for guests, but hefty commissions and poor rates may apply. US dollars in small bills (1s, 5s, and 20s) are invaluable for onward travel to neighbouring countries other than Malaysia, but are only useful in Thailand for exceptional purchases (eg paying visa fees for Cambodia).

Credit cards are widely accepted in the tourist industry, restaurant and shopping mall or widely used in Bangkok and major cities. Fraud is regrettably common though, so use it sparingly and tell your bank in advance, so your card doesn't get locked down because you are using it.
Costs
In a word, Thailand is cheap, and excellent value to boot: the combination of a weak currency, low labor costs and plenty of visitors means that everything a tourist could possibly want is both available and affordable. 800 baht will get a backpacker a dorm bed or cheap room, three square meals a day and leave enough for transport and sightseeing. Doubling that budget will let you stay in decent 3-star hotels, and if you're willing to fork out 4000 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.