I just received my new passport. I will be doing my retirement extension in Jomtien on 5th April. Can I take both old/new passports at that time without doing a transfer of stamps beforehand? Thanks.

You can do them both on the same day.

You can do them both on the same day.

They may expect a letter from your embassy addressed to immigrations to confirm that they issued the new passport ... along with photocopies of all and sundry in your old passport. The US embassy issues the letter automatically. Other embassies ??

Not sure if it's doable on the same day at Jomtien. When I did the transfer I had to return later to collect both passports. Can't recall if I collected later the same day or the next day. Make sure your extension application has new passport information and you should shift your departure card to the new passport if immigrations doesn't do it for you.

Remember to change your passport information with you bank as well so that you will be able to do counter withdrawals and other business with them in future.