You can always go to a Thai bank to exchange your money into Thai Baht. They will take travelers checks but it can be a bit of a problem. Any one getting Travelers Checks knows you have to sign them at the bank you get them at. You are always in a hurry to do this and when you go to cash them in, your signature better look like the first one you put on it or it will be scrutinized. If you use cash the larger denomination the bill, the better exchange rate you will get. Make sure to call you credit card company before you leave too, or you may go to use it and get declined. There are a lot of ATM’s around too, so make sure your card will work internationally.
Some of the major hotels do supply the rooms with 115 volts like the United States but make sure you check first. You can buy transformers that convert 200 volts to 115 volts but they are big and heavy.
Most electronic rechargeable items today will except a wide range of voltage inputs. Things like Digital cameras and laptop computers. Typical ranges on them are 100-240 volts @ 50/60 Hz. Just make sure you check them first.
Do not drink the tap water. Local people seldom drink too. Get bottled water and always inspect the seal to make sure the bottle was not just refilled. If you order water and the seal is broken just politely ask for another one with a good seal. Street side cafe’s and street vender’s, it is a good idea not to use ice also. You should be alright to use ice in all the major hotel chains.
Any 2 star and up hotels will have plenty of things to keep you full if you are do not trust outside food sources. You will not have to be worried of their cleanliness. But if you want to really taste Thai food you can give some of the food stalls and street vender’s a try. Just look to see how clean the cooks and cooking surfaces are kept. I have eaten in some shabby looking places that were clean and have had some of the best food ever in Thailand. If you find one you think you would like to try, just stand around for a while and watch and see how they conduct business. Then see if you want to try what they have to offer. You will never be able to beat the cost also, very cheap and good.