The only time I've been returned change for 1,000 baht as if it had been 500 (at least that I noticed -- I'm not always as careful as I should be) was at a short-time hotel.

I paid with a 1,000 baht note and jumped in the shower. The changed arrived before I had finished, and was received by the Thai boy I was about to enjoy a couple hours with.

A couple hours later, when I picked the change up off the table, I realized that it was short 500 baht. When I accused the room girl, she of course accused the Thai boy of pocketing the difference. A pretty sticky situation, even though the Thai boy opened his wallet to show that he only had a couple hundred in it.

As this particular guy -- although a bar boy -- was someone I had known for years and trusted implicitly, I stuck to my guns, marched up to the managers' office, and gave her a loud berating (in Thai).

Believe it or not, the room girl -- while not confessing outright -- finally took 500 baht out of her own pocket and sheepishly handed it to me. I do not think this would have happened had she not actually been the culprit.

After that, I've always made sure I have exact change on me when visiting short-timers -- where there are not going to be any witnesses present to side with you in case of an argument.