The location where the plane "vanished" is covered by Indonesian and Thai military defence radars and by civilian air traffic radar discussed below. On the site forbiddenknowledgetv we can find the active, civilian air traffic radar map that shows the flight. The map's sidebar shows that the plane made a sharp turn in one direction, then in the other, but not back. It then made an extremely rapid, (physically impossible) descent to sea level, shot forward at great speed and vanished from radar. Of interest here is that on the same active civilian map is the 'target' of a large UFO travelling at approximately 3,000kmh and stopping in the top right hand corner of the map.

Source: The Nation Bangkok September 10, 2016 18:00 UTC