In the title mol-ecule, C(5)H(7)N(3)S, the thia-zine ring shows a conformation close to a half-boat. The Cremer & Pople puckering parameters of the thia-zine ring are q2 = 0.4645 (2) Å, θ = 132.4 (3) and ϕ = 285.52 (2)°. The packing is stabilized by inter-molecular N-H⋯N and C-H⋯S inter-actions.