Will I face immigration issues if I leave Thailand before my extension application is processed?

@Phil *****

you're out nothing by taking your thai wife and going to the immigration office showing that you have a flight out and SEE if there's anything they can do about it.

There's a slim chance they can, BUT it's slim because you already got the 30 day under consideration stamp issued. I know people who when they applied for their marriage extension showed proof they'd be gone for 2 months and had a 2 month under consideration stamp issued so they could get a re-entry permit, leave come back and then go get the year extension.

Good luck with it, as I said you're out nothing by going to the immigration office with your thai wife and trying to see if there's anything they can do. Don't waste the time calling, SHOW UP there with proof you're leaving and see what they say. The worst they can say is "start all over when you come back" (in which case I'd get a new 90 day Non-O visa in the UK before you return so you just have the year extension to deal with once you get back)

OMG... Flying out and having to start all over on return ...hope it does not need to happen.

Nope no problem at all if you leave before the under consideration stamp runs out.