You cannot get a Non-OA in Thailand, you purchase a 12 month extension based on the original Non-O for 1900B by meeting the requirements. In fact a Non-OA is a waste of money as an in country 12 month extension requires the continuation of the mandatory Thai insurance plus the same 800k financials as the Non-O extension so a double whammy.
If you enter with a 90 day Non-O Visa your first 12 month Extension of Stay must be for the same reason your Non-O was issued. After one year your reason for the new extension can be changed by meeting the requirements.
The multi-entry Non-O ceased to exist when the eVisa system was rolled out globally in January. Some Embassies might still mention it because their website maintenance record is shocking.
That's not possible if he wants them to be on a legal permission to stay and to be able to get subsequent extensions. The 800k needs to be in the account 2 months before applying for the 12 month extension then for 3 months after the extension is granted and never fall below 400k for the rest of the year.