There has been discussion recently about the new requirement for 100,000 US Dollars health insurance rather than the existing 440,000 baht cover. As with several others, my insurance company advised that the upcoming insurance renewal on 28th July would need to meet the new requirements of $100,000 cover. TGIA advice was that the 440,000 cover was required for renewals before 1st September 2022. My OAvisa is valid until 30th August despite my insurance expiring 28th July. I pursuaded my insurer, LMG, to reluctantly renew on the old basis. and got a further 12 month permission to stay stamp. Although it did take the IO nearly an hour to process me back in (probably don’t see so many 12 month stamps on a soon to expire visa nowadays).
I don’t pretend to fully understand the changeover from old to new rules but it seems to me that provided you are stamped in before 1st September then the old coverage requirement applies.