Originally Posted by
CPH-Flyer
That's the other way around, the train being delayed, OP was asking about the flight being delayed.
..but it's almost the same vice versa
If passenger is holding a Rail&Fly-ticket (or "Fly&Rail-ticket if the travel starts abroad, issued on a Thai Airways ticket document, he can take any train to/from Frankfurt/Munich airport and as such can travel almost "hassle-free" (you just may want to buy a new seat reservation ticket at Frankfurt Airport Railways station as seat reservations are not included in Rail&Fly-tickets, regardless if First or Coach Class).
Any other railways tickets are under your own responsibility.