When I was considering a similar scenario, I looked at the airports around there and found Kota Bharu to be much closer. The runway may not be similar in length, but if your plane is on fire, you would not be picky.

It is at least 200km closer than Langkawi. The flight path was also close to Kota Bharu, so one theory does not exclude the other.

Maybe somebody with more knowledge of an autopilot can offer some insight: what happens is you overshoot your programmed target? With it go in a holding pattern? Would the autopilot disengage? Or will the plane continue on its course?