Yes, there are shops that will ask for, say 3% (which is not allowed in the US, anyway). It also depends on how many shops are competing. In Tukom and Fortune I have seen many vendors change their tune when I simply say, "OK, I will look for another shop who won't charge me". I pay 5% in some bars in Pattaya but as I mentioned earlier it was a wash for me because I get 5% cash back in restaurant and bars.