Dear Mr.Srinath, for filing a TM application for a foreign client send him the prescribed Form TM 48 on plain paper given in TM Act, and instruct him to execute it and get it notarized in his country and on receiving this POA in India attach a Rs.50/- stamp paper mentioning on it that it forms part of that POA. This is the only requirement for the Trade Marks Registry.
Print the POA on plain paper and send it to your friend abroad. After his signatures (in case of a company, signature of authorized signatory + company's seal is required), he has to get it notarized in his country. After execution and notarization, he may send back the papers. You may get the papers franked here with the Registrar of your jurisdiction.