Okla. Stat. tit. 12, § 591

The trial by jury may be waived by the parties, in actions arising on contract, and with the assent of the court in other actions, in the following manner: By the consent of the party appearing, when the other party fails to appear at the trial by himself or attorney. By written consent, in person or by attorney, filed with the clerk. By oral consent, in open court, entered on the journal.