Straight from Royal Thai Embassy, D.C. website. What I don't understand is that if you purchased an insurance, why showing the insurance is not good enough, they ask you to take an extra step to ask your insurance to sign an document -- Foreign Insurance Certificate Form. Thai government really loves paper works. I am amazed.
TLDR : Answer Summary
The conversation revolves around the anticipated requirement for a Foreign Insurance Certificate when applying for a Non-Immigrant O-A visa in Thailand, indicating that mere presentation of an insurance policy is insufficient. Participants express confusion about paperwork demands, the reasons behind the regulations, especially concerning proof of funds and insurance, and the bureaucratic challenges faced by foreigners. Several comments highlight that the new requirement, effective from 31 Oct 2019, aims to prevent misuse and ensure that applicants can adequately provide proof of their insurance coverage.