If this is my flight itinerary from U.S. to Thailand, at what point will I be asked to show all my documents? Am I going to show the TR visa, COE, COVID test results, Fit-To-Fly, & Insurance in AUS, DFW or DOH? The Thai Embassy states you must present these documents at the "departure airport", but what is the departure airport in this case?

AUS (Austin) --> DFW (Dallas) --> DOH (Doha) --> BKK (Bangkok)