I don't think that South Korea would fall into this category, its pretty well developed and western-style democracy (with some strong nepotic powers at place but ultimately even they are not untouchable).
If you would be invited to say Philippines, Indonesia (which covers Bali too), Myanmar, Laos etc. that should raise an eyebrow.
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.
If you would be invited to say Philippines, Indonesia (which covers Bali too), Myanmar, Laos etc. that should raise an eyebrow.