Yes, people go to M'sia to awol. what docs you need?
1. Passport
2. Exit Permit
3. (optional), Malaysian immigration documents that allows you to
stay long term.
4. Bus, train or air ticket.
AS to the topic question, yes you can downgrade after BMT. but give
it a try, most people regret.
Because the unit OCs usually assume you are "kenging" so they
withhold your OOC/OOT doc. Then use you as fatigue party.
This is a very common practice in SISPEC because people rarely OOT
unless they really injure themselves or not interested in being a
Spec. And since injured people cannot do fatigue duty, they use the
"injured" ones to do the fatigue duties.