Regarding the comments that the Phuket sandbox is now doomed - last I saw, the British were 5th on the list in terms of arrivals, so this will have very little impact. Only if other countries follow suit with similar restrictions on returning citizens will that model be potentially impacted.
Correct me if I'm wrong - If you are fully vaccinated, you can travel to Thailand and spend 10 days in an AMBER country on the way back - does not have to be Green - and you don't ned to self-isolate. The rules changed recently. That gives you a lot more flexibility.