I don't understand your question. It would help if you shared the background as to why the last month's salary was not paid in the first place.
Thoughts on Salary Payment
If he has worked for that period, he should be paid for those days—nothing more, nothing less. Why would you not pay it? Has he done a proper handover at the time of leaving?
Ask yourself, what difference will this employee's salary of one month make to the balance sheet if paid? Is there some special benefit or savings that the organization is going to gain?
If there is a question of fraud, due to which you held back payment, hopefully, you documented it through inquiry and other legal processes.
If the employee absconded, I hope you followed the due legal process of termination, which is clearly documented. In this case, you can calculate the F&F settlement and adjust the salary against the notice period, if any, as per your organization's policy.
I wonder if the other employees think well of your organization when you indulge in such management practices. Overall, please understand that by trying to hold back salary payout unnecessarily, you are hurting your organization's brand image.
Regards,