Chong Pang Camp houses Participation Command which was
previously Air Defence and Operations Command, which was previously
Air Defence Systems Division. Combat units there include 3 DA Bn,
6/9 DA Bn, 18 DA Bn and 160 Sqn. The other 2 air defence squadrons,
163 and 165 Sqn, are in Lim Chu Kang Camp II (opposite the
cemeteries).
But the OP is being interviewed for AOS, which is like others have
said, a non-combat vocation. It's not an air defence vocation. Air
defence specs are Air Defence Weapon (or System, if you're a
regular) Specialists.
I don't think there are any AOS in air defence.
Combat vocationalists don't get to stay out in ADA though. Clerks
maybe, depending on unit.
Likely bases to be posted to are all air bases since you'll be in
the tower.