Do you know what an opinion is?
> as I understand this policy mostly serves to deter foreigners from attempting the potentially very lucrative business of smuggling drugs into Singapore.
So what? That's not a justification.
> Why should they bear this burden for people who have no ties to Singapore and will never contribute anything to it?
Singapore is perfectly able to control their borders better than most countries. It's not like the US where it's relatively easy to sneak in. 'They might come back' is a poor justification for murder.