Your friend wrong lah.
Recruits who enlist will get about $450-$600 depending on which
period of the month they enlist.
The first pay is always alot because it includes $30 (neccessities
allowance). This is for you all the spend on whatever needed for
you for NS, e.g. transport to Pasir Ris Interchange/SFT, bag,
u-wear, etc. So that you wun have excuses of no $$.
Then the pay includes $350 basic allowance.
SAF pays you in advance, meaning... the pay you get on July 10, is
from the enlistment date to July 9 PLUS July 10 to August 9.
Usually this amounts to around $500.
Thru the course of NS, you will have this "lump" payments after
every promotion because your promotion back pay is paid up.