That was a Thai government aircraft, not the property of a Thai airline.
That was disputed at the time and it was the reason why it was stuck there for several weeks, until the Thai Government managed to convince the German court that it was indeed state-operated (and hence had diplomatic status), and not privately owned by the SOB prince who has a habit of not paying his debts on time.
Another instance of an aircraft landing and not departing again on time is the unfortunate circumstance when someone shuffles loose of his mortal coil while on board. Somewhat rare, but it has happened a few times and the plane always got impounded upon landing, no matter how many people it was supposed to leave again with shortly afterwards. It's even worse if the body does not belong to a manifested passenger but is instead found in the hold or some other cavity.