S.D. Codified Laws § 3-13-77

If a participant returns to employment or enters into a contract with a participating employer within thirty days after a severance from employment, no severance from employment occurs for the purposes of the plan. If a participant provided contractual services to a participating employer, severance from employment occurs at the expiration of all contracts with a participating employer, without expectation of any future employment or contractual relationship with any participating employer.