Ok, so its not really magic. But sometimes, I have to blink a few times when I use it. I bought this uber cool bag from the Tassadet (sp?) market down off Mee Chai Road while I was there. I take it everywhere with me now and it seems to expand and contract based on exactly what it is that you want to carry. I packed enough stuff in it for a week at my mom's (clothes, toiletries, walkman and earphones, etc) and this morning, I took it the grocery store and carried five LARGE baking potatoes, three pounds of baby carrots and an onion in it. I didnt want to carry the 4 1/2 lb chicken in it, though it certainly would have fit, with room to spare!
The strap is very long so when I want it to be shorter on my shoulder, I just tie the strap in a little knot to my liking. I love this bag!
People are really buying the reusable bags at grocery stores here and my mom has a couple of GIANT ones from WalMart. But I do not shop at WalMart, and my Magic Bag from Nong Khai is one of a kind...here at least, it is.

The keys are to give perspective to the size of the bag.