Does anyone know if transit passengers flying through BKK but not entering the country are required to have the "medical certificate" and/or "embassy letter" that those entering are required to have? Asking for someone flying from Yangon and onwards to the U.S.
TLDR : Answer Summary
Transit passengers flying through Bangkok (BKK) generally do not need to present a medical certificate or embassy letter as they do not enter Thailand. However, this may depend on the airline, as some, like Thai Airways, require these documents for all passengers, including those in transit.