The Doppler-free high resolution spectrum of the transitions to highly excited states of the (NaK)-Na-23-K-39 molecule was measured by using the technique of the optical-optical double resonance polarization spectroscopy. Several highly excited states 1SIGMA+, 1PI, and 1DELTA were found, and the molecular constants for these states were determined. The vibrational numbering of the 1DELTA state (G 1DELTA state) was estimated, and the potential energy curve was calculated by the Rydberg-Klein-Rees method. Many perturbed lines were observed. The indirect perturbation between 1SIGMA+ and 1DELTA levels through the L-uncoupling interaction with a distant 1PI state was identified. The hyperfine splittings were observed in transition lines to a 3PI state, which is perturbed by a 1SIGMA+ state.