Am i below average for someone in their 30s earning less than 4.5k a month? Is this normal?

You sound like you want to earn more - as long as you are willing to pick up extra skills + responsibilities, study part-time to upgrade, u might be able to reach the median salary of your age.

Normal / not normal - 1) depends on whether you mind (you seem to mind) or 2) whether u mind how others see u.

For me, if I mind, I will put in the efforts to reach my wants, I dun care abt 2 (who's others to judge me since they are not financing me...).
If I dun mind, then no matter what the stats shows, i simply see it as a piece of info that is meant to stir happiness/sadness, full stop and dun move (and repeat when the same info + the median salary grows per year). This info probably is sponsored by those who may benefit from it (e.g. headhunting co./education instituitions), they are not wrong by the way (it's a way to promote their business and in the same way encourage ppl to upgrade).

My industry (private education) mostly earn less than 5 k SGD, so it depends on your industry. I have friends working in tech/analytics earn more than 6 k SGD. So ya. The short answer is it depends on your industry.

The highest percentage of Singaporeans salary are in $3k-$4k range so yeah. Can survive easily without overspending.......

Everyone is different and according to your budget