Is Government office bound to issue another released letter ??

You can get it through R.T.I. application to the concern. 

How can I apply for RTI online?

Visit the official RTI portal https://rtionline.gov.in.

1. For submitting an RTI application click on submit request option.
2. On clicking on submit request option 'Guidelines for use of RTI ONLINE PORTAL' screen will be displayed. ...
3. Then Online RTI Request Form screen will be displayed.

As per your concern let me inform you that section 2 clause (f) of the RTI Act, 2005 has clearly defined the term "Information" which can be obtained with the help of the said Act.
The section 2(f) of the RTI Act, 2005 can be read as follows:- "The word 'information' means any material in any form, including records, documents, memos, e- mails, opinions, advices, press releases, circulars, orders, logbooks, contracts, report, papers, samples, models, data material held in any electronic form and information relating to any private body which can be accessed by a public authority under any other law for the time being in force."

Similar, under Section 6 of the RTI Act any individual can get any information which is already in existence and accessible to the public authority under law. Moreover, under the RTI Act an applicant is entitled to get copy of the opinions, advices, circulars, orders, etc., but he cannot ask for any information as to why such opinions, advices, circulars, orders, etc. have been passed.

Thus, it is advisable to file an RTI to your former office in order to obtain the copy of your resignation acceptance. The process to file the same has already been states by expert Mr. Rama, follow the instructions laid by him to resolve the issue.

Hope It Helps!

Regards,
Kevin M. Paul

what will be subject of the RTI ??? May I write Prayer for getting my resignation Acceptance letter under RTI act 2005

You have to ask them "copy of the letter dated .............. acccepting the resignation dated.......... from the post of ........."