The powers of a county as a body politic and corporate shall be exercised by its board of county commissioners.
It is hereby declared to be contrary to law, and against public policy, for any individual county commissioner, or commissioners, when not acting as a board, to enter into any contract, or to attempt to enter into any contract, as to any of the following matters:
And none of such acts or attempted contracts as above set forth, done or attempted to be done, by an individual county commissioner or commissioners, when not acting as a board, shall ever be subject to ratification by the board of county commissioners, but shall be illegal, unlawful and wholly void.
Provided that nothing herein shall be construed as prohibiting or preventing the chairman of the board of county commissioners from performing such duty or duties as he may be required by law to perform as chairman of such board, but only after the board, by a majority vote thereof, shall have authorized and directed such performance by said chairman.
Okla. Stat. tit. 19, § 3