Every employer, subject to or who or that elects to become subject to the provisions of chapters 29 — 38 of this title, other than a corporation, who or that is not a resident of the state or an unincorporated association, a firm, or a partnership, having no members resident of the state, shall file with the director a duly executed written power appointing some competent person resident in this state as the employer’s agent with authority to accept service of process against the employer in this state and upon whom all process, including the process of garnishment, against the employer in this state may be served, and who, in case of garnishment when the fees for it have been paid or tendered, shall make the affidavit required by law in those cases, and who shall cause an appearance to be entered in like manner as if the employer had resided and been duly served with process within this state. Service of process upon the resident agent shall be deemed sufficient service upon the employer. If the resident agent dies, resigns, or moves from the state, the employer shall file with the director a further written power appointing some other competent person residing in this state as agent for service of process purposes. No power of agency shall be revoked until after a like power has been given to some other competent person resident in this state and filed as provided. Any nonresident employer who or that has duly filed a withdrawal of election to be subject to the provisions of chapters 29 — 38 of this title may revoke the power of agency by a written instrument of revocation filed with the director. No revocation shall be effective as to any liability arising out of any act or omission on the part of the employer occurring prior to the time when the withdrawal of acceptance of the provisions of those chapters became effective.