I had such an experience before covid since the ticket to JP at that time was super cheap. The ground will be waiting for you at the gate and assist the transit when you arrive XMN. However, you must check in the onward flight in HKG as well. It was a bit rush. Now I do CAN instead as the ticket price ex-CAN to KL/BKK are quite attractive. I take speedrail to GZ East then MRT to the airport. Quite smooth so far.