90 Day Reporting...if You Don't Do It...

When is the 2000B fine (or 5000B in some cases) fine given?

Is it when you go through the immigration office to renew your one year visa? Or perhaps when you are getting your re-entry permit?

Someone told me that they are going to start checking for reporting before you get on flights at the airport- fining you on the spot if you have been in Thailand more than 90 days and you don't have the little reciept stapled into your passport.

Any truth to that rumor?

If you have been caught - how did it happen and how much did you have to pay?

Thanks!