Any county establishing an economic development program may contract for the services of an executive director for the program. The executive director shall be employed by and serve at the pleasure of the board of county commissioners; provided, said employment shall be renewed on an annual basis. The salary of the executive director shall be in an amount set by the board of county commissioners; provided, travel and per diem shall be paid in accordance with the provisions of the State Travel Reimbursement Act, Section 500.1 et seq. of Title 74 of the Oklahoma Statutes. The provisions of this section shall not apply to counties with a population of more than four hundred thousand (400,000) persons.