That's not how international travel works until you totally leave civilization; no matter who's paying for the trip, you do know where you're going, and each individual has a choice at every border crossing; they can't simply "export" a box filled with people on a plane that's going "somewhere".
Well South Korean is a peninsula, effectively an island, so you're probably fairly safe there if you don't agree to get on somebody's boat or plane. Accepting a plane ticket to a country like South Korea just isn't very risky. Where you might get into trouble is accepting somebody's invitation to smuggle you across a border, or being taken to a country where the rule of law is in doubt or where you could be driven across a border into such a country.
once your in the air you are effectively detained.
a large number of situations, contrived or otherwise, can result in emergency diversions.
you may want to be sure a connecting flight is legitimate when travelling in 'suspect' regions.
this would be high profile kidnapping, but a source of non SEA persons, that would be more convincing, and a source of international ransom revenues, espescially if they were also accused of some crime.
An airliner being diverted for a kidnapping might happen if a country were trying to nab you, but that isn't a realistic scenario for a criminal gang to orchestrate.