Kishore Kumar, I'm certain, is indeed in this song. Towards the end, at 3:50, the voice that says 'Seth Bandookwala, Tum Log Riha Kar Diye Gaye, Asli Chor Pakde Gaye, Tum Sab Nakli Chor Ho' is Kishore's. Then after that, as the chorus sings La-la-la, Guru is clearly leading the chorus.
In fact, in the movie too, the cop who releases the Seth and his chamchas from the jail is played by Kishore Kumar. Has anyone seen the movie? I've got a VCD of it in very poor quality.