Only light drink available are Cola drinks (Cola Light/Zero and Pepsi Max). In the restaurant check availabily beforehand, many restaurants (even international fast food places) don't offer diet drinks at all. Water is always available.
Because Thai people don't eat much bread by themselves, there is very narrow selection of bread available. Usually just one type of toast.
Prices may change between cities and between seasons. It is a little bit cheaper during (northern hemisphere) summer than winter and small cities are cheaper than big ones.
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