I remember about/at least 20 years ago a fellow drinker from Pattaya was working in Singapore and had been drinking in Boat Quay (Maggie May?), he was calculating his change from a round of 4 and realised it had come to £20.
The barman was watching him and giggling "ha ha you think mistake, think change wrong" he nodded affirmatively and got "ha ha, no, happy hour half price."