We exploit the knowledge of the nonequilibrium potential in a model for the modulated class A laser. We analyse both, the deterministic and the stochastic dynamics of such a system in terms of the Lyapunov potential. Furthermore, we analyse the stochastic response of such a system and explain it again using the potential in a wide range of parameters and for small values of the noise. Such a response is quantified by means of the amplification factor, founding stochastic resonance within specific parameter's ranges.