The Economist measures the relative buying power of different currencies using a "Big Mac" index: It compares prices for the popular hamburger in various countries. Here at corkscrew-balloon.com, it has occurred to us that the buying power of a single currency, in this case the Thai baht, might be measured over time using a slightly different "sandwich" index.
This is a 500 baht note from 1981. Back then, it would buy you a full "sandwich."
This is a 500 baht note from 2002. Due to inflation, your 500-baht "sandwich" today might need to be "open-face."