Experimental observation of the static and dynamic response of monocrystalline lead magnesium niobate, Pb(Mg1/3Nb2/3)O3(PMN), at moderate power c. w. laser irradiation shows five distinct regimes depending on the beamwidth and wavefront curvature of the incident Gaussian laser beam. In one of these regimes, the system exhibits multistability and transient aperiodic regenerative oscillations similar to those observed previously in ceramic PMN. In the other four regimes, thermal focussing and/or defocussing combine with nonlinear Fabry-Perot resonances to produce qualitatively different responses. The thermal relaxation time is calculated theoretically as 1 - 500 s, about 103longer than earlier estimates and in agreement with experiment. Damage thresholds are also discussed.