It is a bit more complicated:
The Constitution of Singapore:
Citizenship by birth
121. —(1) Subject to this Article, every person born in Singapore after 16th September 1963 shall be a citizen of Singapore by birth.
(2) A person shall not be a citizen of Singapore by virtue of clause (1) if at the time of his birth —
(a) his father, not being a citizen of Singapore, possessed such immunity from suit and legal process as is accorded to an envoy of a sovereign power accredited to the President;
(b) his father was an enemy alien and the birth occurred in a place then under the occupation of the enemy; or
(c) neither of his parents was a citizen of Singapore.
(3) Notwithstanding clause (2) (c), the Government may, where it considers it just and fair and having regard to all the circumstances prevailing at the time of the application, confer citizenship upon a person born in Singapore.
So there is the Clause 3, but I would not count on it here too much.