What should I do if my O-A multi-entry retirement visa expired before my return to Thailand?

I think I messed up with my O-A multi-entry retirement visa.

The date of issue was Oct. 6, 2017 and it says Enter Before Oct. 5, 2018. I first entered Thailand Oct. 25, 2017 and I thought the multi-entry was good until Oct. 24, 2018 (tomorrow), after which I would need to buy re-entry permits for my trips out of Thailand for the next year. I just returned this afternoon from a 5 day trip to Myanmar and Immigration at the Chiang Mai airport told me that my visa expired Oct. 5 and that I should have bought a re-entry permit before I left on the trip to Myanmar. (Of course, I did not get a re-entry permit for this trip because I didn't think I needed one when I left for Myanmar on Oct. 18...)

Was Immigration today at the CM airport correct about my visa expiring Oct. 5, 2018?

If so, what are my best options now? I was planning to go to Hong Kong next week and I noticed there is a Thai consulate there. Perhaps I should apply there for a 60-day tourist visa, extendable for 30 days, the go back to my country of citizenship, USA, and apply for a new retirement visa? Any other ideas?