Oh, that's interesting. I had not heard of such cases, nor have I seen them. Do you remember which part of the park this was? I'll keep an eye out next time I am there.
Feel free to walk to Sentosa from HF around midnight. You will find tens of people sleeping around. And yea, they do not have permits of any kind if you'd like to suggest it (neither people sleeping at east coast park have, except people who really do camping there).
Police doesn't care just because Sentosa is pretty much desolated at night, so noone complains or sees them.
There are few other places to mention, way far from HDB/condo settlements in order to maintain a nice picture of homelessness absence.
I left ~5 years ago so I'm not going to guarantee they're still there.
I'm pretty sure the HDB void decks still have their fair share of homeless tho.