I recently found about this watching a two-bit documentary. I scourged for sources but the only anglophone ones all referred to Gregor Strasser and others of his ilk (not very reliable!)
The story goes that Hitler's unit was stationed in Bavaria at the time, and when the Putsch happened, the men of his unit declared themselves loyal to the new government and he went along with it. I find this dubious at best, but they present some photographical evidence and (what ostensibly are) records of him being appointed in one of the soldiers' soviets.
Can't really wrap my head around this. Any light on this would be much appreciated!
EDIT: There's this fictionalized account on Hitler: The Rise of Evil (apparently there weren't any Willy 2 statues in Munich at the time, or ever for that matter). But yeah, they take many other artistic liberties. It's more of a jig for /r/badhistory than anything.
According to the sources I've read on the matter, namely "Hitler" by Ian Kershaw and the Coming of the Third Reich by Richard J. Evans, Hitler did in fact serve the army of the Bavarian Socialist Republic.
That seems odd given that it was a communist revolution, and he was Hitler, but it appears that he didn't partake in any fighting and manage to defect before the collapse of the army and the bloodbath in Munich when the Right wing Paramilitaries entered the city.
I took a quick peak at Hitler's wiki and I'm surprised that isn't listed there. It was a very important event, as lead to Hitler being given ideological training like many other soldiers. It was during this ideological training that Hitler got noted for his ideological extremism and was sent to spy on the Nazi party.