S.D. Codified Laws § 58-33-52
Service of a statement of charges and notices under said Unfair Trade Practice Act shall be made by delivering to and leaving with the director or some person in apparent charge of his office, two copies thereof. Service of process issued by any court in any action, suit, or proceeding to collect any penalty under said Unfair Trade Practice Act shall be made by delivering and leaving with the director, or some person in apparent charge of his office, two copies thereof. The director shall forthwith cause to be mailed by registered or certified mail one of the copies of such statement of charges, notices, or process to the defendant at its last known principal place of business, and shall keep a record of all statements of charges, notices, and process so served. Such service of statement of charges, notices, and process shall be sufficient provided they shall have been so mailed and the defendant's receipt or receipt issued by the post office with which the letter is registered or certified, showing the name of the sender of the letter and the name and address of the person to whom the letter is addressed, and the affidavit of the person mailing such letter showing a compliance herewith are filed with the director in the case of any statement of charges or notices, or with the clerk of the court in which such action is pending in the case of any process, on or before the date the defendant is required to appear or within such further time as the court may allow.
SDCL 58-33-52