Well, it's not exclusively "to Hong Kong", because most of the activity is done online, but I've used a couple of services over the years and have been mostly very satisfied with my current one (virtualpostmail.com), after my previous one (paperlessmail) decided to exit the business at short notice (bastards!).
With VPM you set up a mailbox of your choice at their California office and are notified whenever you receive mail. They scan the front of it for free and put in online for you to see. Then you decide if you want them to open it and scan the contents (which costs a nominal amount per page), which you can then download to your computer wherever you are. If it's something important you can have them ship the letter/package to you wherever you want, e.g., Hong Kong (which, of course, is the real expense). I probably spend about US$50/month all-in, including infrequent mail shipments. Good luck.