It is certainly required to apply for a non-o visa based upon retirement at a embassy or official consulate.
"2.6 Applicant must be medically insured for the entire period of stay in Thailand with the following coverage:
– Outpatient benefit with a sum insured of not less than 40,000 THB, and
– Inpatient benefit with a sum insured of not less than 400,000 THB"
Source: https://thaiembdc.org/2020/11/17/nonoretirement/
Some have changed it to the new $100,000 insurance requirement for a Non-OA visa.