I flew this route almost weekly for 6 months.
They used to use the 34C aircraft on the midday flight to KUL and then the evening flight back to HKG almost on a daily basis. On those occasions, my travel agent was able to book the F compartment at booking but if for whatever reason they couldn't then you have a good chance again if you check-in online early. I've found that most times, if you check in roughly 24-48hrs beforehand, there were usually always some seats available in the F compartment.

However, for the past month (and I assume going forward), it has been replaced by the old 330 (although one time it was the 333) or the 2 class 34D with the 34C only appearing very occasionally.

Note - they do not automatically upgrade MPC to the F compartment. Most of the times I see Oneworld members (BA Gold and AA Plat) in that compartment with some MPC in the normal J compartment.