My experience there was that if you fit within one of the 3 core ethnic groups people would assume your Singaporean. But if you’re in the “other” group then yeah, people would assume you’re a foreigner.

That sounds like HK.

I guess HK and Singapore are multicultural in that you are rather limited in what you can assume is general knowledge.

They don't seem anywhere near as multicultural as places where you hear a wide variety of ethnic groups using the same kind of accent though.