The best way to confuse the controllers in an area where there is no radar, is to make all the inflight reports when they expect them, even if in the blind. Because when you change course, you will naturally be out of radio range at some point from the stations you seek to confuse. But pilots being good guys will relay info for you. About 10 miles a minute at cruise speed, so casual delay in the controller reporting or caring can make you some miles.
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.