We report first-principles numerical discovery of hydrostatic pressure-driven tetragonal to collapsed tetragonal transition in 1111-type material ThMnAsN accompanied by simultaneous magneto-structural, insulator to metal transition together with complete collapse of Mn moments. We present detailed evolution of various structural parameters, magnetism and electronic structures of ThMnAsN with increasing hydrostatic pressure. All the structural parameters show anomalies at a critical pressure Pc∼ 8.1 GPa; c-lattice parameter, out-of-plane As–As bond length, anion height (hAs) undergo drastic modifications compared to the in-plane parameters which is manifested in an iso-structural phase transition from tetragonal to a collapsed tetragonal (cT) phase. These modifications in “local structural correlations” due to pressure destroy the usually localized nature of Mn moments which gets completely quenched. Apart from that the elastic constant, the electronic structures also bear the finger prints of insulator-metal and magneto-structural transition at higher pressures accompanying a total collapse of magnetic moment at the vicinity of Pc. The critical value of the pressure Pc at which tetragonal to collapse tetragonal phase transition occurs, remains robust with respect to the on-site Hubbard correlation (U). The dynamical stability of the compound at higher pressures (above and below the magneto-structural transition) is affirmed through detailed computations of phonon dispersion curves endowed with positive phonon frequency throughout the Brillouin zone. The effect of magnetic spin structure on the electronic band structures is obtained through band unfolding. The electronic structure of ThMnAsN at higher pressures “orbital selectively” influences bands, band gap and closely resembles with the electronic structure of Fe-based superconductors (quasi-two-dimensional Fermi surfaces) with the occurrences of orbital-selective Lifshitz transition.