The Great Gambler (1979)

Jai is an expert gambler who works for the underworld don, Ratan Das. He gambles with rich and influential people so that he can win huge amounts of money from them and in the process tricks them into doing what he wants. He manages to do so with an employee of the government and obtains certain confidential secrets of the military. When the police get to learn of this they send down CID inspector Vijay to investigate but the problem is Jai and Vijay are look-alike and to make matters worse both of them are mistaken for the other by the underworld, their colleagues and even by the police.