Okla. Stat. tit. 58, § 58-162: Nonresident representative must appoint agent

Every executor, administrator or guardian appointed in, but

residing out of the state, shall, before entering upon the duties of

his trust, in writing, appoint an agent residing in the county where

he is appointed, and shall by such writing stipulate and agree that

the service of any legal process against him as such executor,

administrator or guardian if made on said agent shall be of the same

legal effect as if made on himself personally within the state. Such

writing shall give the proper address of such agent and shall be

filed in the office of the judge of the district court where such

appointment is made.