Now for the most likely scenario and endpoint.
So an oxygen bottle ruptured which took out the exact systems that tracked and communicated the aircraft’s position but left every other system necessary for flying the aircraft perfectly intact? Somehow a gradual decompression (even though any fuselage rupture would cause a more than gradual decompression) that went unnoticed by the crew, causing them become unconscious before the cabin altitude warning went off for the first time in history (or did this magical explosion specifically knock out the cabin warning too?). They were aware enough to program a track to Aceh over Penang but too incapacitated to descend, the slightly more critical thing. And then an hour after this magical decompression managed to program the FMC or change heading to turn 90 degrees south past the northern tip of Sumatra, even though in your own story you admit the pilots are dead at this stage?
I suggest you read up on Occam’s Razor.