Well obviously if your purpose is to change course in an unauthorized direction, then you have to stop reporting at some point. And if you continue to report after you change course, that would give away your new bearing. Would it not? So that kind of defeats the purpose. Seems to me right before the change off is a logical time to stop reporting, and change course if you want those precious few minutes to get as far away as possible.
I see the Malaysians passing off control of the plane to the Vietnamese, the Vietnamese accepting, but then sitting there waiting for the plane to signal for a few minutes thinking the Malaysians passed control too early(or something). And all the while the plane has now drastically changed course back to toward the Malaysian coast. But the Malaysians have already taken the flight off their board of responsibilities.
If someone has the equipment. This isn't a military operation, it is something out of the ordinary. The guy working the radio on the ground is expecting ordinary, when he gets it all is well. I could already be flying the opposite direction when I report. The ground guy won't expect another report until I near the next Estimated Enroute Time for the next FIR (Flight Information Region). In this case the Ho Chi Minh boundary with either Hanoi or Sanya.
I see the Malaysians passing off control of the plane to the Vietnamese, the Vietnamese accepting, but then sitting there waiting for the plane to signal for a few minutes thinking the Malaysians passed control too early(or something)
In that area, I doubt there is the radar capability for that process. Looking at the FIR boundaries and the graphic depiction, it looks like the flight turned short of the FIR boundary for the Nam and was in an area where three FIRs converge.