Ifleeplanes:
Do they not have conditioning air available in Bankok?
since all our routes are central Europe
That last point explains it, then.
Bankok can be one very humid, warm, sticky place. Put a 747 loaded with 400 pax on the tarmac and there is no aircon unit on earth that would keep the plane anywhere near comfortable, or even acceptable. If you still have the choice, You shouldn`t go there without APU IMHO.
Sorry for the slight side-step from the thread.