Singapore Airlines KrisFlyer - Standby on Connecting SQ Segment

I'll be flying SYD-SIN-HKG all in SQ J with checked luggage. My itinerary is now giving me a 4 hr layover in SIN then taking the last flight SIN-HKG. If I decide to go standby (*G in J), but I have checked luggage, will SQ allow me to do it provided there is a seat in J?

No. You need to get your ticket reissued first before SQ will allow you on..