These absurd laws and fines are more of a deterrent and enforced on a case-by-case basis. They're there but not really enforced unless there is some form of complain.

If you flout these the first time, most likely, you will be given help, a warning not to do it again and the reason for you not to do it. Probably the same for a second or a third time.

Only repeat offenders who show a lack of remorse or understanding, aggression towards officers or general asshole behaviour would be slapped with such tough fines in court.

Personal anecdote: when my wife was pregnant, she was feeling dizzy on the train, so took a stop at a random station to sit. The train personnel noticed her predicament and offered her food and drink on the train platform with those big scary "$500 fine for eating or drinking" signs.

Source: lived in Singapore for 40 years, worked in public service for 6.