The title compound, C16H19N3O 4S, is almost planar, with a dihedral angle of 2.88(9)°between the mean planes of the benzene and thiazole rings. The molecule adopts an E conformation about the two C=N bonds, with a C-N-N-C torsion angle of -177.01(11)°. An intramolecular C-H⋯O hydrogen bond exists between a thiazole methyl group and the formic acid ethyl ester carbonyl O atom. In the crystal, molecules are linked by O - H⋯O hydrogen bonds, forming chains propagating along [2-10]. The chains are linked via C-H⋯O hydrogen bonds with R 2 2(12) ring motifs, forming sheets lying parallel to (12-2). The sheets are further linked through out-of-plane C-H⋯N hydrogen bonds with R 2 2(12) ring motifs and C-H⋯π interactions, forming an interesting three-dimensional supramolecular architecture.