Is health insurance for Non O-A visa sufficient for COE application in Thailand?

You will need to get two lots of insurance unfortunately

As previously stated: same company and same policy is possible but be aware that you have to meet the minimuml requirements for COVID as well as for the Non O-A visa, resulting in acoverage for inpatient at 100'000 Dollars and coverage for outpatient at a miniumum of 40'000 Baht. Be also aware that if you choose a non Thai company, you will not be able to extend your visa after one year within Thailand (or you will have to change companies again or buy an additional policy from a Thai company that meets the minimal requirement for extension).

You need two insurances for the OA, but some insurance companies are combining the two into one policy

need 2 letters ---

For the COE, you must have a statement from the insurer that you are covered up to USD 100,000 for COVID