There's a thread on GB which is well worth a read but I thought I'd start one here. My experience of getting the 'wrong change' in Thailand is rather limited but then I virtually don't drink so I'm not a good example. The coins wedged inside the corner flap is well known as is the 100 less than it should be when paying with a 1000 baht note. If buying petrol make sure the pump is set to zero before the attendant fills up. More of the station's now have pumps where the amount is keyed in before the filling starts.