(a) In this section, a "proxy coupled with an interest" includes the appointment as proxy of:
(1) a pledgee;
(2) a person who purchased or agreed to purchase the shares subject to the proxy;
(3) a person who owns or holds an option to purchase the shares subject to the proxy;
(4) a creditor of the corporation who extended the corporation credit under terms requiring the appointment;
(5) an employee of the corporation whose employment contract requires the appointment; or
(6) a party to a voting agreement created under Section 6.252 or a shareholders' agreement created under Section 21.101.
(b) A proxy is revocable unless:
(1) the proxy form conspicuously states that the proxy is irrevocable; and
(2) the proxy is coupled with an interest.