In the crystal structure of the title mol-ecule, C(13)H(15)NO(5)S, the S and N atoms of the thia-zine ring exihibit the maximum deviations from the least-squares plane of 0.3008 (6) and 0.3280 (7) Å, respectively. The ring therefore adopts a half chair conformation. The thia-zine ring is twisted by an angle of 13.29 (7)° with respect to the aromatic ring. The isopropyl substituent is oriented at a dihedral angle of 53.2 (12)° with respect to the thia-zine ring. An intra-molecular O-H⋯O hydrogen bond occurs. Inter-molecular hydrogen bonding is observed in the crystal structure.