Originally Posted by
dutchkiwi
Because when I fly TG the miles will be credit to TG , and when I fly with SQ, the miles will be credit to SQ,
You don't have to credit miles from TG flights to TG, or miles from SQ flights to SQ. You can pick one *A programme and credit miles from flying other *A airlines to that programme. In this way you may be able to retain your *G.
I know, for the upgrade i can use point i accumulate by the airline i booked.
You can also use points/miles collected in one programme to upgrade on flights on other *A airlines.