If the Heading for Bejing was 18* N then a 180* reverse plot towards Kuala Lumpur course would be 198* S.
I would be one of those thinking that the pilots made the adjustments and then succumbed to smoke or decompression.
The plane would have then run into the area where they suspect the plane went down(out of fuel)?
yes....ok, well there is no indication, that the aircraft headed back to KL....the proper procedure for an aircraft in trouble is to fly out of the air corridor,as other aircraft could be flying on the same track and then by turning 90 degrees to the track, and leave the air route....this what appears to have happened...the aircraft did turn 90 degrees and headed west...