to go low level in cloudy conditions when you know there are big mountains around is pretty stupid
I was wondering that one too, as the report indicates they had only an High altitude en route IFR map not showing terrain, and not a visual map .
But if you read the CVR carefully , from 07:30 44 the Capt says " No problem with terrain at this moment " the guest replies : yeah , it is flat " could indicate the Capt knew there was terrain around.
They only planned to fly 20NM around the VOR and there is indeed no problem in that area.
What was not planned is the fact that the aircraft left the plannned orbit which was above flat ground unoticed by the crew.(demonstrating a Holding input on the FMC ) and headed towards teh mountain.
The rest of the conversations show a crew confused as to which heading they should take to return to Halim , which ironically is also the location of the VOR they are tuned on !
Difficult to understand .