(a) Notwithstanding Subchapter C of Chapter 659, trustees who are contributing members of the retirement system serve without compensation but are entitled to reimbursement for all actual and necessary expenses that they incur in the performance of official board duties.
(b) Notwithstanding Subchapter C of Chapter 659, subject to the approval of the board of trustees, trustees who are not contributing members of the retirement system may receive:
(1) compensation; and
(2) reimbursement for all actual and necessary expenses that they incur in the performance of official board duties.