S.D. Codified Laws § 34-26-74
A person, who is 18 years of age or older and of sound mind, by entering into a preneed contract as defined by § 55-11-1, may direct the location, manner and conditions of disposition of the person's remains, and the arrangements for funeral goods and services to be provided upon the person's death. The disposition directions and funeral prearrangements that are contained in a preneed contract are not subject to cancellation or substantial revision unless the cancellation or substantial revision has been ordered by a person who the decedent has appointed in the preneed contract as the person authorized to cancel or revise the terms of the preneed contract, or unless any resources set aside to fund the preneed contract are insufficient under the terms of the preneed contract to carry out the disposition directions and funeral prearrangements contained therein.
SDCL 34-26-74