I took a look at the satellite images. It's a bit hard for me to gauge what the entire area that is supposed to comprise 900k people is, but the official numbers for Pyinmana (inside the capital district but not the capital itself) is about ~100-200k, and Pyinmana is visibly more dense than the city of Naypyidaw itself.

In contrast to Brasilia (which is perhaps the most well-known recent-ish create-a-new-capital-from-scratch initiative), it is far less dense and less occupied. Contrasting to most of the other newer similarly-situated capitals, Naypyidaw is clearly pretty poorly populated and some of its infrastructure is laughably oversized compared to what use it would actually get (Why do you need that road with 10 lanes in each direction? It goes from nowhere to nowhere...).