What is the procedure for using an old passport with a DTV while entering Thailand?

Most passports become invalid once you get a new one. Many countries even require return of the old passport first so that it can be corner cut or otherwise indicated as no longer valid, before they will give the new one, regardless of whether the reason for getting it is because the old one expired, or is damaged, or is running out of pages. Is that not the case for your country?

The BIG question is

Do you have an eVisa <- that is a PDF file the consulate emailed you which is your actual visa that you got when you applied online thru the eVisa system

OR

Do you have a "sticker visa" <- that the consulate stuck IN your passport when you applied in person for the visa

IF you have the eVisa and get a new passport you need to have the print out of the DTV visa PDF, copies of the data page of the old passport and your last DTV entry stamp from the old passport, you show those with the new passport when you go to stamp IN to thailand and you'll get stamped in on the new one no problem

Where as if you have a sticker visa, you carry BOTH passports (because the visa can't be moved from the old passport to the new one and you have to show the VISA every time you stamp in). They will see the visa in the old passport and stamp you in on the new one

If you've been issued a new passport, the old passport is invalid. You can use it, but if the system shows it's invalid, expect some serious problems