Bangkok Branch branch in Patong that my account/debit card is with has closed down according to Google.

 

When I arrive for a visit next week, do I just go to the nearest available branch with my passbook/passport and they will "adopt" (i.e, transfer the account info to their branch) the old account, or will it be the usual T-idiocy PITA  and require an entirely whole new account opening?

 

I could care less about having an actual branch since I don't live in Poo-crap anymore. The debit card, which I never use, expires in a few months - assume the app will keep working regardless? As long as the app keeps working, I don't really GAF.

Your account will have been officially relocated to another branch. You have to go there and get a new passbook. I think you should call Bangkok Bank and ask them which branch is your new one. 

They won't transfer your account to another 'home' branch if it's only a temporary closure, which on their website only list Kamala branch as temporary closure https://www.bangkokbank.com/en/Locate-Us#tab1

 

last time I had branch closed and transferred to another branch I was able to keep the old passbook and account numbers 

 

These days there are only a few things that can't be done unless you're at a *home* branch - getting new passbook in case of lost books

fixed term deposits most other things can be done at any branch