Short Ninja, your son should be eligible for renounciation of
citizenship without having to serve NS, as he has never enjoyed
"benefits and privileges of citizenship", and has stayed for less
than 10 years prior to enlistment age.
What normally happens would be that MINDEF will grant him a
deferment until he is 21, then he can exercise his
renounciation.
Better to check with the Embassy or MINDEF though. This is what
I can recall offhand.
actually, i dont think he can renounce as yet.
taking myself as an example, i must either renounce or pledge
myself by my 22th birthday (they give you a year's grant to make
such a decision starting from your birthday)