singh is king ji

It is Gurbani -- and Sara has given the linguistic explanation for this. Why not post an example of where you saw this with the surrounding context so we can take a look and see what might be going on? I sounds to me as if someone did not understand the idea of the oblique form as Sara explained.
Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/gurmat-vichaar/20073-difference-between-gurbani-and-gurubani.html
Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/showthread.php?t=20073

I had a second thought. The person may be trying to say Guru's Bania -- but unsure of the 's rule. This is very hard when learning English.