It's a joke.
Around tourist areas they are known to balance the pump handle in such a way it doesn't reset to zero on the pumps used for scooters.
Tourist comes in on a rented scooter, either tells them to fill it up or get 100 baht of gas, it starts at say 50thb instead of 0 baht, and the attendant then gets to skim the 50 baht.
Have you just arrived in Thailand or what?