It's a bit confusing, with the article saying international flights are suspended, but Delhi Departure and Bangkok arrival show flights between the two cities:
https://www.bangkokairportonline.com/flight-status-arrivals-.... From there, a flight to Frankfurt leaves at 2300.
The EU also pooled their repatriation flights. He could have gotten on any French, Italian, Spanish etc. transport, space permitting.
There's obviously something wrong with this guy. And if there wasn't before, six weeks at an airport made it happen. He should just go home and for it to be credited as time served.