As Mr. Rao has pointed out, it is very difficult to prosecute the company without any proof. When you don't have an offer letter or bank statement, it is challenging to establish that you are an employee of the firm.
If you have an official email address and have had exchanges with your boss on any official issues, it might provide circumstantial evidence to support your employment at the company. However, please note that when you pursue legal action, this email ID may be deactivated. Additionally, a copy of your attendance statement could be helpful in such situations.
These options are viable if you are considering taking legal action against the company for non-payment of salary, especially if the dues exceed 50,000. While you can pursue claims for amounts as low as 5,000, anything less than 50,000 may not be worth the legal battle considering the time, effort, and stress involved. It may be more practical to seek alternative employment and move on from this situation.