6 month multi entry tourist or 60 days tourists, but not a good long term strategy. Or send 800k to a bank in Thailand and leave it there. Get a 90 day NON O and then enter Thailand. Extend for a year and get a multi re-entry permit. Come and go when you want. Extend every year while in Thailand.
So in your post you state that insurance is needed for an OA and ask about it, and then in the comments you state that you have a NON O. Why ask about insurance for an OA if you don't have one??
Should be fine if arriving with more than 6 months and not intending to stay long term (an exiting flight itinerary will help with that) BUT they may question it.