Dear Mahendra,
Post-retirement employment under the same employer or elsewhere can be of two kinds viz., employment once again under a fresh contract of service OR engagement under a distinct contract for service. In the former, employer-employee relationship continues and so are the applicable conditions of employment signifying the status of the person employed as an organic part of the organization whereas there is no employer-employee relationship in the latter indicating the status of an external stake holder only.
In other words, if an existing employee is retained in service after his retirement on attaining the age of superannuation whether as a fixed term employee or as a regular employee, he is entitled to all employment benefits as applicable to other employees.