I would very much appreciate any information on this dilemma:

I hold a UK passport with 6 years, but with only a few unused pages, left - in this is my extension of stay based on retirement, which expires in two months.

I also have an Australian passport, with plenty of unused pages and 7 years till expiry.

When I come to renew my extension of stay, will I be able to do so using my Australian passport? If so, I can avoid having to renew my UK passport. This would be the easiest option.

If I can't switch over to the Australian passport, I will have to renew my UK passport when next over there (later this month), which I understand can be done in a day with the necessary financial inducements. I can't renew it in Thailand, as I have to travel more than once a month, so it will take too long.

What is the procedure then in terms of coming back to Thailand using my extension of stay, which will still be in my old passport?

How long before expiry of the extension of stay should I go to extend it?

Thank you.

If you want to switch passports you have to leave the country and get a visa in the other passport.

Upon re-entry into Thailand show the old passport with extension of stay and re-entry permit. At the airport they will stamp you in on the new passport and tell you to visit your immirgaiton office to have the details transferred.

tku vm for your help