Mo. Rev. Stat. § 252.130: Failure to pay fine and costs — procedure.

Whenever upon conviction the person convicted fails to pay the fine and costs imposed upon him, he shall be committed to the jail of the county or of the city of St. Louis or to some workhouse and shall there be kept confined one day for each two dollars of the fine, and not more than twenty days for costs adjudged against him, unless otherwise paroled by the judge of the circuit or criminal courts of the state as otherwise provided by law in criminal cases.