I posted an almost identical thread on the 5th with no answer, and it still was not addressed in this thread. When transiting through Narita you have to clear a security checkpoint before you even reach the airline transfer desks. At this security checkpoint you need to have something to prove you are a transiting passenger. This becomes the tricky part for your connection as a jumpseater. You wont be able to get anything printed off in the states regarding your next jumpseat attempt to BKK to show at the transit checkpoint.

I just got back from Indonesia via NRT yesterday and had listed myself on a family friends UA companion pass, and checked in for the NRT-SFO sector in TPE to prove to NRT transit security I was had an onward ticket and had no problem. Had the flights actually been open where I could have jumpseated, I would have asked the agent to remove me from the DM list and put me back on as an OMC. But I was not that lucky and had to take the $218 hit on the pass. You could do almost the same thing with a ZED fare with UA/DL, and once at the gate in NRT, just ask to ride OMC. In reality this is your best option because going through NRT without a ZED to back up on NH or JL is insane in case you hit one of those ruts where each flight has 30 plus non revs like what I just witnessed this week.