Any suggestions for health insurance for Americans in Thailand?

Go to the hospital in Thailand you plan to use, and ask them for their list of insurance companies they have direct billing contracts with. Then work down that list to pick a provider that meets your needs.

If you pick an insurance provider that is not on their direct pay list, you will have to prepay for medical expenses out of your own pocket, and then wait to be reimbursed by the insurance company.

If cost is an issue, consider a plan that does not cover you in the US.

https://www.bumrungrad.com/en/patient-services/insurance-we-accept