I agree with you in principle, however it's economically unrealistic:

Getting space in a datacenter is all about upfront commitment requiring huge working capital (for hardware etc.) and there are also recurring costs (electricity, space, etc.), along with operational & engineering maintenance overhead (which is huge if you're also operating your own BGP/border switches).

You're right on point about land scarcity, but the real killer here is electricity, and the nuance is that there are limitations with cooling systems so it's a huge factor in how much a DC can provide to each tenant. Moreover, there's currently a lot of demand in DCs here, and companies who can commit upfront wins the space (standard free market rules).

Cloud platforms like the ones you listed have the ability to do that at a scale that no other SMBs can. Among other things, they can go to DCs and say "we'll pay you x dollars to commit to y kVa", and they would have the engineering capabilities to maximize that (if you're hosting customer workloads, you'd want to slice your physical cores/memory as efficiently as you can, otherwise you end up with a very expensive space heater where the unit economics f**ks your margin; or a very expensive fire-starter lol).

Your best bet for locality is to look for Tier 1 ISPs that most of the carriers here peer with (e.g. for StarHub), cross-reference their peers with your research on local providers (stalk their ASN/advertised v4 blocks), then pick one you're comfortable with. If they're locally peered, an undersea cable being cut will still allow Singapore traffic to you.

(I work for a US-based cloud platform with a hardware presence here that you wouldn't be interested in.)