If Singapore's Chinese plus Malaysian population = 91% of the country, I consider that an ethnostate. I can't pick out differences between two Asian nations that are so close together, any more than I can visually pick out the difference between Austrians and Germans. Saying that French and Swedes can live together is a different thing than saying Zulus and Boers get along well.
Are there any examples of multicultural societies between the major racial groups (Caucasian, Negroid, and Mongoloid)?
So Singapore is an Ethnostate without the need for any need for explicit racial policies.
High barriers for entry and meritocracy does the trick. An actually functioning Civic Nationalist State that ends up being a de facto Ethnostate.
I don't think there can be such a country without a dominant ethnic group that enforces the rules for others that would work.