Can I apply for a Non-Imm O visa for retirement in Thailand instead of an O-A?

Hi everyone. I have some mundane visa questions that don't involve Covid 😁

I plan on retiring to Thailand next year, but I'm trying to find the right approach. I'm not asking about the documents required at this stage, as I can obtain whatever is needed.

I would rather use a Non-Imm O visa rather than O-A as I understand there is no health insurance mandate on the former, and I'd rather self-insure at this point.

It seems one process is to apply for a 90-day Non-Imm O at my local embassy, enter Thailand and then apply for the year extension based on retirement a month before that expires.

However, the Visa form provided by the embassy does not have a box to tick for O or O-A. Does that mean they might try and force an O-A on me?

And if they do, can I change an O-A to an O when the time comes?

I can't seem to find clear advice on this.

Or do you have any alternative suggestions?

Thanks in advance.

(Oh, and I'm looking at Chiang Mai).