How easy/difficult is it to find a fried insect stall at Bangkok thailand, and how much are they?

You won't have much of a problem, although you won't find them everywhere. You're much more likely to find a cart selling them then you will in a fixed stall. There is a bug cart that sells them right off Sukhumvit on Soi 4 that is there most every night, and has a pretty good selection of beetles, grhoppers, worms etc.. I've tried a few and liked the white larvae grub worms or whatever they are, the best, very crunchy and kind of tasted like wood. Many vendors will let you sample the bugs before you buy or can set you up with a variety pack, the prices are very cheap, as little as 20-25 baht depending on how much and what ones you buy. Have fun.