As we are hearing now...you will need to either buy health insurance from the Thai approved list/link. Or submit a signed Certificate of International Insurance from your current insurer showing your health policy meets the minimum requirements of the O-A visa.
If do you not have this insurance, upon arrival to Thailand, Thai Immigration likely will stamp you in for 30 days. During which time you can purchase the health insurance and go to Thai Immigration to submit the Certificate from the insurance company showing you now have the insurance. Upon doing so, your permission to stay date will be adjusted to that of your O-A visa stamp.
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