Okla. Stat. tit. 74, § 1307.3

Unless the Oklahoma Health Care Authority has otherwise contracted with an out-of-state provider, the Authority shall pay for medical services and treatment rendered by an out-of-state provider at the same level paid to an in-state provider if the insured was referred to the out-of-state provider by a physician or it was an emergency situation and the out-of-state provider which offers the type of services needed is the closest provider in proximity to the place of residence of the employee.