Directors of health provider cooperatives are elected under procedures set forth in chapter 10-15. A member may vote by mail for a director unless mail voting is prohibited for election of directors by the articles or bylaws of the cooperative. The board of directors shall prescribe the form of the ballot. The members shall mark the ballot for the candidate chosen and mail the ballot to the cooperative in a sealed plain envelope inside another envelope bearing the member’s name. If the ballot of the member is received by the cooperative on or before the date of the regular members’ meeting, the ballot must be accepted and counted as the vote of the absent member.