Tips on Thailand! Calling all Aussies!?

I'm going to Thailand (Bangkok, Phuket) for a short holiday and was wondering how I would use my money over there. Do I get my cash exchanged at a bank over here? (Living in Australia) Or is it safer to use some kind of card. I don't have a credit card, but are there any cards to get which can be used all around the world? I'm really confused!! Please help!!