Seems very strange that immigration said you should have a visa given you are from USA and presumably don't have a history of entering Thailand without a visa, but this is Thailand as they say.
You do not state which IO you will use, but your wife should have no problem applying for the non O.
apologies for joining this conversation, but your response is very clear, concise and well informed, so I wanted to ask a silly question as I am unclear.
I receive a work pension from the UK and I pay tax on it, so I believe the DTA applies.
Do I need to do anything in Thailand to show that I already paid tax?