Okla. Stat. tit. 58, § 58-28: Proof of notice - Waiver of notice

At the time appointed for the hearing, or at the time to which

the hearing may have been postponed, the court, unless the parties

appear, must require proof that the notice has been given, which

being made, the court must hear testimony in proof of the will. If

such notice is not proved to have been given, or if from any other

cause it is necessary, the hearing may be postponed to a day

certain. The appearance in court of parties interested is a waiver

of notice.