In fact, if you book upgrade on the web, you can still get it before getting the YBHK ticket first. However, you still need to ticket to confirm the upgrade before the deadline - and do not wait until the last moment to do so.

The flight availabiltiy on Asia Miles web page may not always be accurate, but if you can get through to the end and get the confirmation response of your booking, then you should be in good shape. Again, remember to ticket your underlying ticket (if not already done) to reconfirm before the deadline.