I’ll agree with Suntou’s points 2-6.
The first point – gambling is illegal. There is no specific legislation referring to online gambling, however the Chinese government is known to crack down on online gambling as well.
The 7th point – the bit about CAC Macau – is debatable. The Mainland Chinese market is viable – however, you really have to know your way around, this is not going to be an easy market for any non-Chinese to crack. It has nothing to do with communist ideology theory.
Hong Kong is technically not a viable market as online gambling is explicitly illegal with the sole exception of the operation run by the Hong Kong Jockey Club monopoly.
Macau is way too small a market to target and of course people will naturally prefer to play in the land-based casinos there as far as table and live games are concerned – and will generally avoid slots anyhow.
In short – unless you have a Chinese partner, you would be well advised to not waste much energy on targeting Mainland China. Foreigners (with rare exception) are not going to know enough about how to reach that market, whether they live in China or not. The same goes for most of Asia, with the exception of countries where English is widely spoken, such as Singapore and Malaysia.