Okla. Stat. tit. 36, § 2807

After any such association is organized and has commenced business, its membership shall be composed of its policyholders only, and every person accepted as insurable shall be ipso facto a member. Noncompliance with the bylaws and nonpayment of assessments within thirty days after request so to do shall forfeit member's policy and membership; provided, such member shall be held liable for his pro rata share of any liability existing at the time his membership is forfeited.