Okla. Stat. tit. 58, § 351

If the personal representative is a creditor of the decedent, his claim must be presented for allowance or rejection to the judge of the district court not later than the presentment date as provided in the notice, and its allowance by the judge is sufficient evidence of its correctness, and it must be paid as other claims, in due course of administration. If, however, the judge rejects the claim, action thereon may be had against the estate by the claimant, and summons must be served upon the judge of the district court, who may appoint an attorney at the expense of the estate, to defend the action. If the claimant recover no judgment, he must pay all costs, including defendant's attorney's fee.