This is part of what I did with my Hong Kong company. It used to be possible to end up with zero tax this way, but took a lot of work to get there. I remember hearing something about the US-China tax treaty removing Amazon/Paypal zero withholding status from Hong Kong, Macau and Taiwan. Make sure there is still a way to do that before going forward with it.
Assuming you can still get to zero tax with a HK setup, it will be a constant struggle to maintain. Even though you aren't paying taxes in HK you still go through all of the paperwork, auditing, etc. etc. etc. as if you were. Technically speaking your zero tax status is reviewed every year and it will always be on you to prove that you don't owe taxes. In this aspect HK is no better than the US or EU. You will always end up getting bills for things you didn't know were legally required too. Whatever you think your fixed costs of owning the company will be, don't be surprised if it ends up being triple that every year. If you're doing less than US$30,000 in annual profit your total cost of doing business will be lower by setting up an offshore company somewhere cheap like BVI and eating the 30%,
While not zero tax, Russia still qualifies for 0% withholding from Amazon. Their corporate rate is 15% and you can effectively make that zero by sending money to companies you own in other countries. Something else to consider: you can get Russian citizenship from owning a company for 3 years, but will have to employ some Russians and pay some taxes to get there. Given the quality of the Russian passport it's a steal at twice the price.