Retiring

Not if you have a visa.

I plan on getting one when I get there

If no visa before you depart home country the airline should not board you because they would be liable for returning you home should Thai immigration refuse your entry.

If you have a proper visa before leaving you should not be a problem.

I will have to figure something out then. I work in the middle east, stay in Dubai when I have a holiday but am a US citizen. I have no resident visa for UAE.

You could buy a cheap throwaway ticket to a neighbouring country to Thailand and show them that.
e.g.. Bangkok to Phnom Penh is about 50 dollars.

A one way ticket is irrelevant to a retirement visa. It is a separate issue. I would suggest making further enquiries.

I plan on being there later this and retiring next May. I will confer with some more people, I dislike dealing with lawyers though any suggestions. I usually go to Pattaya.