Mr Singh, who is speculated to contest the Lok Sabha elections on a BJP ticket, attended a party rally in Uttar Pradesh's Meerut today and shared the stage with BJP leaders like Amit Shah. He also addressed the rally briefly before BJP's prime ministerial candidate Narendra Modi arrived.
The day he resigned, the 59-year-old top cop had said, "So far my sphere of work was limited to Mumbai, now I want to serve the country. I want to focus on working for social harmony, national integration and world peace."
The 1980 batch IPS officer belongs to Meerut and there is speculation that he could contest from there. Media reports also said that he had an offer from the Aam Aadmi Party.
Mr Singh is the first serving Mumbai Police Commissioner to resign. He was due to retire in 2015.
He is a post-graduate in chemistry and also has an MBA from Australia and a PhD in Public Administration.