SDCL § 61-1-20: Foreign service for employer with principal place of business in state included.

The term, employment, includes the service of an individual who is a citizen of the United States, performed outside the United States except in Canada, in the employ of an American employer (other than service which is deemed employment under § 61-1-26 or 61-1-27 or the parallel provisions of another state's law), if the employer's principal place of business in the United States is located in this state.