In reply to your question, as long as you have an address in the Far East, you can register with Asiamiles programme. If you are to move from Far East to say Europe, your Asiamiles membership will be temporarily suspended and you'll be transferred fully to the Executive Club UK.

If you're with Asiamiles, you'll earn mileage with Asiamiles and also get BA Tier points. Asiamiles can be earned by flying Cathay or other OneWorld Alliance partners, shopping or even through credit card(all Hong Kong based).