The most legal way....
get out of singapore before you are 11.5 years old, get a
citizenship elsewhere. This way, you are not liable for NS and you
still can come and go out of singapore.
The "shady" way,
get out of singapore before you enlist, you are technically not
awolling, but you are in breach of the enlistment act. You get into
trouble upon your return to singapore.
The "stupid" way,
while serving NS, take leave to go overseas, and never to come
back. Awol 6 months and you face desertion charge.
it seems you have been asking questions relating to serving NS the
"alternative" way... can i help you in anyway?