A. An employee whose membership in the retirement system is contingent upon his own election and who elects not to become a member may thereafter apply for and be admitted to membership, but no such employee shall receive prior service credit unless he became a member within sixty days after July 28, 1948.
B. The board of trustees may, at its discretion, deny the right to become a member to any employee who is only partly paid by a parish or city school board, or who is paid by any other agency or any local government, or who is occupying a position on a part-time or intermittent basis.
C. A member ceases to be a member if he:
(1) Is absent from service more than five consecutive years and has credit for fewer than twenty years of service.
(2) Withdraws his accumulated contributions.
(3) Withdraws from active service with a retirement allowance.
(4) Dies.