Online check-in experiences with RTW tickets
 

I would like to arrive at KUL at midnight on a ticket which is not part of my AONE4. The onward MH flight leaves at 9am the next morning. I prefer to not re-enter Malaysia since I will have visited that country the previous week. My plan is to do an online check-in for the MH flight departing from KUL. When I arrive in KUL, I can stay airside and use the transit hotel. Has anyone been successful with online check-in using MH, especially for a ticket issued by AA? It is not an AA codeshare on MH and I am a US citizen.

Not sure on online check-in (but MH don't appear particularly advanced on these things).
I'd think you'd have more success at transfer desk (next to hotel) or with the staff at the MH lounge.

Worst case clear immigration in the morning, turn around and checkin.
Ive done plenty of multiple entries into Malaysia in a short period, both at KLIA and the SG/JB crossing