Most places deal only with cash. Some foreign credit cards are accepted in high-end establishments.
Tipping is not generally expected in Thailand, though it is appreciated. The exception is loose change from a large restaurant bill – if a meal costs 488B and you pay with a 500B note, some Thais will leave the 12B change. At many hotel restaurants or other upmarket eateries, a 10% service charge will be added to your bill.