Can I return to Thailand on October 12th or 13th with a re-entry permit if my 30-day stamp expires on October 11th?

I would check my re-entry permit, as long as it valid you can enter

Your current permission ends October 11th. As

@Tod ********

said, you cannot enter Thailand after October 11th.

Suggest you fly back to Thailand before that date and visit your Thai Immigration office to obtain the One year extension during the week before October 11th.

You're confusing a couple things..

First you don't have a one year anything, you are on a 30 day under consideration stamp it would appear 🙂

What lets you get back into the country is the re-entry permit expiration date

SO how about you look at the re-entry permit stamp and see what the valid until date is?

you have to enter ON or before that date to get stamped in and you will only get stamped in until your current stamp (the under consideration stamp) is valid for

SO you can't enter AFTER that date. It's not relevant at all when you can show up at the immigration office to get the new year extension stamp inked in. That has no bearing on you comin' back IN to the country before your current stamp/re-entry permit runs out

And the fact you got a new passport has nothing to do with it, other than they'll stamp you in on the new passport and you'll get all the stamps moved when you show up at the immigration office on Tuesday the 15th of Oct.