OK, I'll try.
If I've understood correctly, the flight lost contact while it was crossing a fairly narrow corridor of airspace that is covered neither by Malaysian nor Vietnamese civil radar. Is this correct? If incorrect, mods, please delete post.
At this point, some catastrophic event is surmised to have occurred that caused all other forms of communication to fail. At the same time, there is as yet no evidence of an explosion, an in-flight collision or any wreckage at this point.
The coincidence that this surmised event happened during the 'radar-blind' corridor crossing is, logically, either relevant or irrelevant.
If relevant, then all sorts of wild theories, such as plane theft, become less implausible. But that nice Mr Occam and his razor tell us to look for simpler theories. The 'civil radar blind corridor' is, presumably, a fairly widely known phenomenon. Who might make use of this corridor? Various militaries, presumably. Is there evidence of illegal / unregistered / unrecorded aviation in the region and at this altitude?