Wilcox County District Attorney Michael Jackson said a judge found probable cause in the case and bound it over to a grand jury Tuesday. Jackson said the victim, 17, and an ex-sheriff testified in court.
The case will be presented to a Wilcox County Grand Jury in June.
Thomas, a former Alabama state representative, was placed on indefinite administrative leave from Wilcox Central High following the arrest. His position as principal has since been filled by someone else.
Thomas remains free on bond.