Thailand has six denominations of coin:
* 10 baht -- aluminum bronze center, cupronickel ring
* 5 baht -- cupronickel (silver colored)
* 2 baht -- aluminum bronze (gold colored)
* 1 baht -- cupronickel (silver colored)
* 0.50 baht -- copper-plated steel (copper colored)
* 0.25 baht -- copper-plated steel (copper colored)
(The early 2 baht coins were cupronickel and hard to distinguish from the slightly smaller 1 baht coins. I've not noticed any for a while. The easiest way to distinguish them was that some commoner wrote "2" on the coin with a marking pen.)
The two small coins, worth respectively slightly more and slightly less than a U.S. penny, are seldom seen. Post offices sell small envelopes for 1½ baht each: I always bought an even number lest I be cheated out of ½ baht. (I never thought to bring a ½-baht coin along to see if they'd accept it.) While you'll only see whole numbers in most venues, big chains like 7-Eleven do have unrounded prices. If your purchase comes to ฿100.25 and you don't have exact change, you're expected to come up with ฿101. And then do NOT expect any change if the teller has no tiny coins in her till. Occasionally the up-country 7-Eleven which I visited regularly waived the ฿0.25 with the receipt containing some blurb extolling 7-Eleven's generosity!
These days, most payments are made by pointing one's phone at a QR-code. Such payments are not limited by coin availability. As an experiment I confirmed that I can send someone ฿0.01 (about 300 microdollars U.S.) with no service charge.
Thailand has a 7% VAT, but you almost
* never need worry about that. The price you're quoted -- usually a round number -- INCLUDES the VAT. On the receipt the VAT is shown as 6.542% (.07/1.07) of the quoted total price.
* - Exceptions include some of the most expensive restaurants and hotels. I guess they figure their customers won't notice or care about taxes and service charges added on here and there.
More likly stores will just price their goods at the nearist 5c. and round the sales tax.
That's difficult to do in California. If you're selling goods from a van, the tax rate will change when you enter or leave a district which needs to pay off its library or sewage bonds, and a third rate may apply if you deliver to an address a few blocks away. Whether an orange drink is taxed may depend on the precise amount of its fruit content.