Thank you all for the information, feedback, and recommendations.

Yes, I did have one visa exemption entry (thank you for the correction).

I have no overstays and no extensions. I leave the country on the morning of or morning before my passport stamp expires. I am only required to be out of country for 24-hours (I believe this is still correct as of the last time I read the Thai Immigration regulation), but have a mini vacation with my wife for 4 days before my return.

Copy on having 20K Thai Baht in cash when i return to Thailand.

I was polite and didn’t argue with the check-in representative. I even asked her to repeat what she had said to ensure i understood.

All of my flights and travel plans are paid for and I have printouts of all of my travel, my health insurance, and bank statements (in case I am asked about my financial disposition).

Copy on the “proper visa”. I am newly retired and planned on upgrading to a marriage or retirement visa after entering Thailand on my 90-day Non-Immigrant O visa. However, I found out after entering the country that the U.S. embassy does not provide verification of pay letters. I do not have 400K or 800K Thai Baht to put into the bank. Not sure about that one yet, still weighing options.

So, with that being said, when i return to the U.S. I will apply again for a proper visa.