You need a COVID test with Etihad.

Not a major problem on the way into Thailand, although you need to satisfy whatever time rules both Etihad and Thailand have. The Thai requirement to have a result issued within 72 hours of the first flight departing is quite flexible.

However, if you were flying from Thailand to a country that doesn't need a COVID test, the Etihad rule gives you the additional expense of a test at the end of the trip, not to mention the risk of having to quarantine in Thailand instead of going home.

As for insurance being accepted, well get a copy of the policy documents and read them to see if they explicitly mention coverage for COVID and a sum insured. If OK, you stand a good chance.