Right now there are no requirements for insurance for an O-A visa. There was talk of implementing such a rule on 1st July but it is yet to happen.
You say "extension". If you mean that you are going to extend at immigration, with either 800k in the bank or 65k a month income, there is no rule and currently no plans to implement one.
The health insurance requirement that was talked about is only for obtaining a new O-A visa from a Thai consulate in your home country.