S.D. Codified Laws § 7-8-11
Upon such redistricting, as to any member or members of such board whose term or terms of office extend for an additional two years beyond the next election, the tenure of office shall not be affected, and in redistricting the county such board shall designate the district or districts to be represented by such member or members, the district or districts so designated to be a district or districts which would elect a commissioner at the next general election following that to be held in the year of such redistricting. Such commissioner may or may not be a resident of the district he is designated to represent. Each district for which representation is not provided by such designation or designations shall, at the next ensuing general election, elect a commissioner, the term of office to be determined as provided in § 7-8-1.
SDCL 7-8-11