Krisflyer won't care if you fly SQ or not ... so don't bother. They will only care if you spend at least SGD $25 K a year, and then you'll be PPS.

If you're already *G with AC, then just show your card for the benefits and credit your miles to either start-from-scratch Krisflyer or TG's Royal Orchid Plus. With the latter however, they do give out one upgrade coupon upon qualifying and their programme is quite good too.

Krisflyer is only good when you redeem SQ flights online and you get a 15% discount. No upgrade certs, nothing else.