Do I need to leave Thailand every 90 days on a Non-O visa or retirement extension?

Brandon is totally correct. Here is a checklist you can use; one additional item needed was a google map printout showing where I lived.

you have to report (online or at local immigration) every 90 days. You do not need to leave the country every 90 days on a retirement extension. You don't actually every need to leave if you choose to keep extending

Get a Non-IMM O on line. The Consulate in Van is very good and they are very helpful. Once you get there you can easily get it extended for 1 year. I am in Pattaya and the Immigration in Jomtien have very specific Instructions on what is needed to extend and how to do it. I have no idea how other Immigration offices operate though.

I suspect he was talking about a multi entry non-o visa whereas you just want the 90 day one

NEVER ask someone at an embassy about visa matters handled by immigration inside Thailand and never listen to what they have to say.

Similarly never ask an immigration officer about Thai visa matters at an embassy or listen to what they have to say.

They are two completely different government agencies that know nothing about each other and do not communicate with each other.

If you get the 1 year extension based on the 90-day non-O you certainly do not have to leave the country every 90 days.

If you get the non-OA you're going to have a much more difficult application with the embassy and you're also going to be stuck with a very high insurance requirement, basically forever.

Disregard what you were told and continue with your plan. Get the non-O, travel to Thailand and open a bank account ASAP, deposit your money and go to immigration after the money has been in your account for 2 full months.