They have a lot of injured/suspended midfielders so I suspect Singh will drop back down to the reserves soon. I hope he can keep his place on the bench though.
Bayern don’t play again until late Jan, so yes that maybe it, as far as match day squads go with the first team.
BM II play tomorrow in Munich, in their own last match before winter break so wouldn’t surprise if he played for them.
BM II have fallen away a bit of late, to be only 2 points off the drop zone.
I'm sure the club, would much rather have their young players like Singh playing at as high a level as possible for their development ie Liga 3 where there are some bigger historical German clubs like 1860 München, Dusiburg, Kaiserslautern, Waldhof Mannheim - rather than down in the 4th tier, which has nearly 100 clubs spread over 5 regional divisions (pub football).