It is technically possible for underground stations to be at
street level. The ticketing and passenger service facilities can be
built next to the street, with escalators leading down to
platforms. However, I have yet to find any in Singapore. Teh
closest is Bishan.
Anyway, I don't remember having to take many flights of escalators
at Chinatown. It seems to have the same number of escalators from
street to platform as Bugis.