would it really come to mind to someone who wants to hide to shut down the ACARS? To shut that down first and then ten minutes later, the transponder? The opposite sequence would make so much more sense. Or both roughly at the same time.
Sure:
-- You're the bad guy. The a/c is at TOC, so it's time to get to work hiding.
-- After the TOC message is sent, shut down ACARS first, since you're still in Malaysian ATC radar coverage.
-- A few minutes later, once the handoff to Vietnam's ATC is attempted by Malaysian ATC, you go further dark by turning off the transponder(s).
-- You're now invisible to ATC secondary radar, the handoff was never completed, and you've bought yourself some extra time since neither Malaysia nor Vietnam can see the a/c (except for a primary target).
-- Do whatever voodoo it is you need to do.