Hey there,
I would advise you to travel to HKG for Stage 1, because if you choose to do so, you will be offered a concrete chance for an interview. The same cannot be said of a possible interview in KUL, as they probably have already drawn up a list of candidates to assess there. Additionally, I personally don't think that changing your interview location preference at such short notice will go down well with the HR team, if you previously indicated you could come to HKG but now want to go to KUL instead.
Furthermore, if you stay in the Headland you could be saving a lot on transportation and accomodation costs as well. I know that staying in a hotel for 10 days straight isn't exactly the best thing to do if you're going somewhere for the first time, but as far as an interview goes you are both close to the venue and already saving a lot of money that would be used on transportation to and from CX City and the airport. Depending on the lengths you are willing to go to, your financial expenditure could be much lower than you are probably anticipating. You might be paying peanuts by going to KUL for Stage 1, but going to Stage 1 in HKG has its own unique strengths at a cost that I personally think is reasonable. That's just me though, you be the judge!
My two cents, hope it helps!