The EU can't reach over into another country and start applying their laws unless they are willing to invade. The only way the EU has to enforce this law is if you interact with them, so they can physically block or take your assets, or if your government thinks that the EU laws should be applied at home, in which case why are you complaining to the EU?

There is no world police enforcing laws in every country. It all boils down to a monopoly on violence and if a country can't physically get to you or your stuff you can tell them to fuck off all day

I think the spirit of GDPR is to target the multinationals who also have tax dodging subsidiaries the world over. E.g. The EU could calculate global revenue for Facebook and then fine Facebook Ireland (or wherever) the resulting sum; which Facebook Ireland would be legally obliged to pay. But I am speculating

Edit for clarity

If they can enforce their data protection laws on the global net, why can't they enforce their 'hate speech' laws on the global net?

They do. For example, Twitter filters out Nazi related hate speech in Germany and France.

What happens if you have no presence in the EU and the EU tries to fine you? How do they actually get you to pay the fine instead of just ignoring it?

You just become persona non-grata in the entire continent of Europe.

The company can't make business deal with europe. People owning the company are fine and can't visit with no fear of being annoyed by the police, the EU is not the US.

What organization is responsible for fine enforcement?

If such a fine is levied, but the company is based in China, does China have any treaties with the EU demanding the fine be enforced, or can they tell the EU to go pound sand?

Yesterday I was presented with WeChat's Cookie policy for European users [1] for the first time, and they appear to have a European subsidiary, which could probably be fined. Of course they could just decide to fold that operation, especially considering (IANAL, but) the policy doesn't appear fully GDPR-compliant. I doubt that they are making significant profit in Europe anyway.

[1] http://www.wechat.com/mobile/htdocs/en/cookies_policy.html

GDPR could become a global thing, because it could be used by the EU as a predecent for Free trade agreements. (which most nations in the world are happy to sign).

It could, but with controversial concepts like "right to be forgotten" baked into the GDPR, I don't assume most nations will necessarily be happy to sign "free" trade that requires them to rewrite history records.