I'm wondering the legality of such a scenario. A Thai Limited Company that provides website design sees an opportunity in UK market, and decides to create a wholly owned subsidiary in the UK. This UK subsidiary starts an online poker information website on a .co.uk domain name, and blocks all Thai IPs from accessing it. The UK subsidiary then sells advertisements or performance based commission deals to market online poker to UK residents. It follows all UK laws and pays UK taxes.

Stop scenario here and ask question: Is there any legal issues in Thailand with a Thai Limited Company owning this subsidiary, if all work on gambling is conducted from the UK and Thais can't even access the information site?

Expanded Question: What if the entire project was managed from Thailand, UK subsidiary paying it's parent for management, maintenance and SEO services, and Thai staff accessed the site via a VPN to do the updates. Does this add new legal challenges?

Appreciate if anyone has knowledge on this topic and is willing to share it.

I think you will have to check with an expensive international lawyer rather than a free web forum in order to stay out of legal trouble.