1 minute ago, rwill said:

Otherwise you might be looking at leaving Thailand reentering visa exempt and then appling for a new non-O.  

 

If you are on overstay already that could complicate things depending on how long it has been.

Overstay since 27th May.

Depends on Immigration, after paying an overstay fine, will allow him to apply for a new 1-year extension, or insist he obtain a new Non O.
He'll have to exit and obtain that from a Thai Embassy/Consulate.
 

immigration normally never give an extension beyond passport end date

Whatever the case, I hope the OP will post back to let us know what he did, and how it worked out. 

 

That's for future reference, to benefit anyone who finds themselves in the same situation.

 

12 hours ago, tac said:

I can't "immediately obtain a new passport" it takes 6 - 8 weeks, and there is no expdited passports for people applying outside of the country. 

I presume you did already contact your Embassy?  They can issue an emergency passport quickly if needed.

 

"If you have an urgent need for a replacement passport and can show proof of imminent travel, we may be able to issue you a limited-validity emergency passport within 72-hours at the discretion of consular staff. Also, if no appointment is available, you may be able to appear during appointment hours without an appointment at the discretion of consular staff. It is recommended you appear at 7:30am Monday –Friday (except U.S./Thai holidays or the last Wednesday of the every month).

Please note: An emergency passport has only 5 pages, maximum 1-year validity, and is issued under special circumstances.  The validity cannot be extended and pages cannot be added."

Get a new passport asap. Then visit immigration to get the visa transferred into the new pp and have all the docs ready for the 1 year extension. Play dumb when they notice they made a mistake giving you a extension beyond the May date. Play on their mistake and you acted in good faith etc. They can fix it they want to, bend the rules however they see fit. If you are lucky they will sort it out. 

 

If not you may have to pay a fine and hopefully not be black listed. Depart Thailand and get a new  o visa. Return and go through the process  of a new retirement/marriage extension.