(a) An employee shall not be entitled to be paid compensation for total incapacity under chapters 29 — 38 of this title for any period during which the employee was gainfully employed at an average weekly wage less than that which he or she was earning at the time of his or her injury notwithstanding an existing agreement or decree to the contrary. In that instance, an employee shall be entitled to benefits as provided in § 28-33-18.
(b) In the event that an employer or insurer has made payment of compensation benefits to an employee during any period during which the employee was not entitled to be paid in accordance with subsection (a) of this section, the employer shall be entitled to credit for any payment of compensation made during that period of employment against future compensation benefits payable directly to the employee.