A word of warning - total costs of doing business in Hong Kong are much higher than you would expect from doing a little reading or you will be lead to believe by people wanting to sell you company registration services. The worst part is that the expenses are not transparent or clearly explained; they will just act like it is obvious when handing you a bill for something you never knew was required. Even if you operate completely outside of HK and do not owe any HK taxes you still have to file complex HK tax documents that are roughly as invasive as anything you would find in the US or Europe. Something I know from experience that doesn't get mentioned until you get the bill is that part of your HK tax filing requires you to have your accounts audited by an accounting firm in HK. This is a huge expense that provides no value for a very small business. Hypothetically let's say you sell on Amazon and get one monthly payout from them, so there are total of 12 deposits on your bank statement. Expect to pay at least HK$15,000 (maybe more) for those 12 deposits to be "audited" in a way that will be accepted by the IRD with your tax return. My auditing bill (with less 200 annual transactions) was always higher than all other expenses of owning my HK company combined (annual fee, registered agent, mail drop, bank fees, etc.).
Tax-free =/= headache-free
When you add in the fact that China has completely disregarded its agreement with the UK not to meddle with Hong Kong until 2047 I cannot recommend Hong Kong as an offshore jurisdiction under any circumstances. Singapore is still 97% of everything Hong Kong used to be and is what I recommend to people thinking about Hong Kong for tax purposes.
Before PT Shamrock disappeared they had a setup for a company account in the Philippines that didn't have any reporting or tax obligations for about 2000 USD. Now that PT Shamrock is gone I don't know who has the contacts to make that happen, but it might be worth looking into.
edit: Over the last 5 or so years it has become a lot harder to open decent bank accounts in both HK and Singapore. Sure, you can technically have HK company registratiion done in a day, but an account at HSBC to actually collect the money? Not so much. Do yourself a favor and pay more for a service that takes care of getting you an account with a decent bank along with providing registration services. If it saves you a plane ticket and 2 weeks of hotel expenses it doesn't really matter if they want an extra $500 or $1000 to facilitate the bank account.