I recently got a new UK passport while in Thailand. My last covid extension (expires in May - I will leave Thailand beforehand) is still in my old passport. Do I need to get the covid extension transferred to my new passport or can I just exit showing both passports?  The old passport now has the corner cut off to indicate it is no longer valid.

Immigration at the airport will transfer your permit to stay that the extension allowed that is in your old passport to your new passport and stamp you out of the country in it. 

When checking in for your flight you will need to show both passports.

5 minutes ago, ubonjoe said:

Immigration at the airport will transfer your permit to stay that the extension allowed that is in your old passport to your new passport and stamp you out of the country in it. 

When checking in for your flight you will need to show both passports.

Thanks. Would all that be done at the normal immigration counter, or do I need to go to some office there and allow extra time for that?

31 minutes ago, mark147 said:

Thanks. Would all that be done at the normal immigration counter, or do I need to go to some office there and allow extra time for that?

It will be done by the officer at a normal departure immigration desk.

Perfect, thanks. One final related question: When filling out a form (at purchase) for VAT refund, should I give old or new passport details (or doesn't matter)?

24 minutes ago, mark147 said:

When filling out a form (at purchase) for VAT refund, should I give old or new passport details (or doesn't matter)?

You might need your old passport to prove the amount of time you have been in the country or for proof you are legally in the country.

Yeah, perhaps they need to see the old passport (for the visa) but how about in terms of which passport number to put on the form?

Funny how inconsistent it can be though, I got charged an overstay for not getting the retirement extension (visa) transferred to my new passport when I did the new extension (a week before it ran out). That was at CW not the airport.

5 hours ago, George FmplesdaCosteedback said:

Funny how inconsistent it can be though, I got charged an overstay for not getting the retirement extension (visa) transferred to my new passport when I did the new extension (a week before it ran out). That was at CW not the airport.

Don't understand.

You cannot obtain a new extension until your stamps and visa information is transferred.

 

The stamps are transferred by immigration (free service) then the application for extension processed. 

 

I along with many others have done exactly that at CW.

How much were you charged for overstay. 

14 hours ago, George FmplesdaCosteedback said:

Funny how inconsistent it can be though, I got charged an overstay for not getting the retirement extension (visa) transferred to my new passport when I did the new extension (a week before it ran out). That was at CW not the airport.

I am pretty sure the fine was not for overstay. Most likely, you were fined for a failure to submit your last required 90-day report.