I doubt that any conscript based army is able to keep such a secret if any halfway capable foreign intelligence service wants to know more about it.Since all our guys are or were conscripts, we know that anything not declassified, should remain that way - which means everyone is in on the same secret. Isn't getting everyone in on the secret a good way to keep the secret?
The nature of conscription is that everybody gets in. And with this one is always going to have some rotten eggs in your basket.
Not to talk of possible leaks in the foreign countries you train in.
I would think of it more of an open secret with which the public (foreign one it is) is fed in order not to put more oil onto the fire of a possible arms race in the region.
I would be surprised if Singapore's neighbours are utterly surprised when suddenly Cents run out of the warehouses in case of war.
The same applies for every other big ticket item in a conscript army.