You have to think for yourself whether you want a US citizenship
or a Singaporean citizenship as Singapore does not allow for
dual-citizenships. You can't have it both ways. However, if you
take up US citizenship without completing your NS,
you will be liable to get charged and fined/jailed if you ever set
foot in Singapore again, since I understand that you currently hold
Singaporean citizenship.
I have a friend who was in a similar situation, except that it
was between Australia and Singapore-- he did his NS, den emigrated.
This way, he can still come back to Singapore to visit friends and
family without fear. Besides, military service is looked upon
favourably in US and Australia, and is actually a pretty big plus
in your CV/resume.
Hope this information helps you =)
My advice mirrors Edwin3060's.
I would suggest you serve NS first, and then decide if you wish
to take up US citizenship (i.e resume) or take up Singapore
citizenship. There are a few reasons why this would be a better
choice.
You mentioned you have a NRIC and Singapore birth cert, that's
pretty much a lot against you at the moment should you choose the
first option.
Let's say you decide to leg it, and head back to the States and
claim your US citizenship and live your life there. If for some
reason or another, your career requires you to travel to South East
Asia and Singapore, this might be a disadvantage since it is very
likely you will have to return or have an opportunity to do so,
especially for work and so on.
Do you want to have this issue sticking to the back of your
head? It hardly seems logical nor positive.
If you serve NS, you get a chance to decide legally and freely
what citizenship you wish to take up after completion. Don't worry
about serving NS as an American citizen, there's a fair number of
foreign-born NSFs these days.
In my time, I had Japanese, Russian and Australian platoon
mates in BMT.
Lastly, I would highly recommend you speak to the consular
section of the US Embassy as they have assisted many such
cases at the moment. They can help you to ensure that you stay on
the right side of the law and also advise you on your nationality
claims.
(FYI to the rest, please stop the blame game and leave
your petty envies and hang-ups about the threadstarter or his
situation to yourself. He is asking a legitimate question here.
Thank you. )