Entered the country with a valid SETV in an old passport. Handed over both passports (new and old). No problems. It just occurred to me whether I have to inform immigration about the new number or can I just wait until my time of extension. Thanks.
TLDR : Answer Summary
A user inquired about whether they need to inform Thai immigration about their new passport number after entering the country on a SETV with an old passport. Commenters suggested that the new passport number might have already been provided upon entry and recommended bringing both passports when applying for an extension.