retagging happened for me in the past for CX-SQ connection. And if I am correct, all of the airlines other than CX uses HAS? So they should also provide the service?

Otherwise I would still say the time being sufficient. If I guess correctly you are flying CX845 to HKG connecting to TG603? CX845 usually arrives early and it arrives at a time where there is little queue at immigration (while the baggage claim can be a hit or a miss). The walk to T2 is quick is you know the way. As I usually arrive before the Arrivals open 0530 off CX845, I would say the time is sufficient