they'll ask him to serve full time NS first.
after that, they will say there's this law saying you cant throw away singapore citizenship before completing at least half of all the required ICT cycles.
So no point throwing anymore once he served.
only way is to not be born in singapore and for him not to hold any pink or blue ic, till he is old enough to be exempted (no age limit is specified).
Once born in singapore, its mandatory he become a singapore citizen. Cannot choose.
If born overseas, later on can still choose whether he wanna be a singapore citizen and serve NS.
Another possibility: if choose to bring son out of singapore to avoid NS, get a foreign citizenship without throwing singapore citizenship. Then dont ever come back to singapore again in his lifetime. else need go to jail first.
Link for reference:
https://singaporelegaladvice.com/law...nent-residents
remember. if you want your son to become vietnam citizen (since we are in a vietnamese related topic here), he will also likely need to serve NS in vietnam when that time comes.
if you ask me to choose vietnam or singapore to serve, i would choose singapore. Because at least singapore is high income country and can buy HDB with discounts and grants.