S.D. Codified Laws § 58-16-3
The employees eligible for insurance under a policy issued under § 58-16-2 shall be all of the employees of the employer, or all of any class or classes thereof determined by conditions pertaining to their employment. The policy may provide that the term "employees" shall include the employees of one or more subsidiary corporations, and the employees, individual proprietors, and partners of one or more affiliated corporations, proprietors, or partnerships if the business of the employer and of such affiliated corporations, proprietors, or partnerships is under common control through stock ownership, or contract or otherwise. The policy may provide that the term "employees" shall include the individual proprietor or partners if the employer is an individual proprietor or a partnership. The policy may provide that the term "employees" shall include retired employees. No director of a corporate employer shall be eligible for insurance under the policy unless such person is otherwise eligible as a bona fide employee of the corporation by performing services other than the usual duties of a director. No individual proprietor or partner shall be eligible for insurance under the policy unless he is actively engaged in and devotes a substantial part of his time to the conduct of the business of the proprietor or partnership. A policy issued to insure the employees of a public body may provide that the term "employees" shall include elected or appointed officials.
SDCL 58-16-3