Okla. Stat. tit. 6, § 6-1720
Establishment of additional offices by out-of-state
institutions.
An out-of-state trust institution that maintains a trust office
in this state pursuant to Sections 15 through 20 of this act may
establish or acquire additional trust offices or representative
trust offices in this state to the same extent that a state trust
institution may establish or acquire additional offices in this
state pursuant to the procedures for establishing or acquiring such
offices set forth in Section 13 of this act.