They literally have an immigration schema, if you want permanent resident to citizen track, that requires immigrants to match the ethnic makeup of the country's citizens.
So you have all these white public housing advocates, talking about how great public housing is in Singapore, but they leave out that you have to have PR or citizenship to get it, and they've accomplished making all that possible by having like half their population non-citizens who pay taxes for housing they're ineligible to get and then the people living in the public houses are ethnically guaranteed non-replacement.