No salary and less salary than minimum wages.

Post your query in simple language, it is vague.

Many Acts are applicable for your father. But I suggest as you are determined to take action on this, it is better to seek a paid up conference with an Advocate and justify your seriousness.

Better to approach a local lawyer 

You may approach an NGO in the area looking after the welfare of the Labour and labour related issues so that there shall not be attendant expenditure just to get guidance.

Let your father approach District Legal Services Authority and through them get instructions to Labour Inspector for finding out the facts and they will suggest a suitable remedy.  You need not spend one rupee for all this but at the same time, there is no guarantee for further employment as the trust may take a decision that he is unfit to perform the duty due to his old age etc.  It is time for you to take care of your father who was working for more than 45-50 years for his family.  Perform your duty as a son first, before asking the employer.  Keeping an employee for 45+ years is itself  a great favour and disclose the sincerity of the employee also.

Thank you for your advice. I am performing my duty as son as I am running my family as he is not being paid since last 1 .5 years. I just want to ensure that he is paid for time spent. Anyways, we wanted full and final settlement. That's all. Regards 🙂