The riverside area near the Bridge on the River Kwai is lined with restaurants catering to tourists, many of them floating on the Khwae Yai river. Quality is variable but the setting is pleasant. Most places serve standard Thai food — pad thai, green curry, tom yum soup — alongside some Western options.
For something more local, head to the night market near the city centre, where vendors sell grilled meat skewers, fresh noodle soups, and seasonal fruit at very low prices. The market is busiest from early evening until around 10pm. The area around the bus station also has good cheap Thai-Chinese noodle shops popular with locals.