About USD and THB
US Dollar (USD)
The US dollar is divided into 100 cents and is used in the United States and several other economies, and many tourist businesses elsewhere quote prices in dollars. When a card terminal in another country offers to charge you in dollars, that is usually a dynamic currency conversion with a poor rate; choose the local currency instead.
Thai Baht (THB)
The Thai baht is divided into 100 satang. Thai ATMs charge a flat fee for each foreign-card withdrawal, so a few larger withdrawals cost less than many small ones. Street stalls and markets mostly want cash, while malls and hotels take cards.
Exchanging USD for THB
The rate above is the mid-market rate for USD to THB. Banks, card networks and exchange desks usually apply a margin or a fee, so compare the amount you would actually receive. If a terminal offers to charge you in USD instead of THB, decline: that conversion normally uses a worse rate.