Regarding Covid Insurance to enter Thailand in the amount of $100,000 USD; here is website recommended on aesianow.com by ubonjoe (expert).

https://www.tipinsure.com/CovidRegional/product_detail

Available up to 99 years old. Cost is not dependent on age but on length of stay from 4800 THB for 30 days to 43,200 THB for one year.