It is over 20 years already since I first heard of the Japanese rule of fours: Four inches, four minutes, four thousand baht.
That was in the time that a BF was 200 baht and I paid one thousand baht LT (plus breakfast if she wanted it, offered in the morning, wasn't mentioned in the deal). And I still stick to the Dutch rule of ones: One foot, one night, one thousand baht 😉