If you dislike the whole bargaining thing and don't like being ripped off all day long I suggest doing just about all your shopping at Tesco or BigC or Carreforre, prices are fixed just like at home, prices are low, usually lower that any shops or markets outside (which is why you'll see thousands of Thais shopping at these large super stores) furthermore you can bring back faulty good for a full refund within 7 days (try doing that at a market)
When eating at restaurants prices are usually listed with the dishes, however, if they are not you must ask how much everything is, or else you'll be charged more for being a farang. You see when Thais charge us extra they don't see it as a dishonest thing, they believe it is the correct thing to do, because they see their government charges farang 200% - 400% more that Thais at the national parks and major attractions.