What are the experiences of expats using FEHB Anthem/BCBS at Bangkok Hospitals?

Yes many under contract especially the big quality hospitals like Bumrungrad and Bangkok Hospital.

Just call BCBS to get Guarentee of Benefits GOB where they commit to pay hospital. Or sometimes since the hospital works with BCBS all the time the hospital insurance department will call BCBS for the GOB ...but sometimes they drop the ball.

I usually pay for the initial doctor consultation B1500 on my credit card and submit the claim to BCBS overseas portal. Then if you've got a major medical procedure you can get the scheduled date and call BCBS and/or the hospital insurance department 1-3 weeks ahead of time.