Yes. You start from square one again. You apply to transfer from visa exempt to a Non O for 2,000 baht (you’ll need at least 15 days left on your stamp. Jomtien might require 21).
When that’s winding down you apply for the yearly extension (and get a multiple entry re-entry permit at the same time to save future hassles).
Yes you enter visa exempt and when you have 30 days left (some offices allow 45 days) you apply to convert to a Non O at your local immigration office. Cost is 2,000 baht.
You do need to have the 800k in a Thai bank in your name only to do so.
That will give you a 90 day visa and when that’s running down you apply for the year extension.
For the second and subsequent years you can switch to the 65k transfers method.
You would have to bounce out (doesn’t have to be by plane) and re-enter to get the full year stamp.
You can’t convert to an O from an OA. When your OA is done then you can leave and return on a new Non O or if your passport permits a visa exempt stamp and convert to a Non O in country.