Ab initio based relativistic configuration interaction (CI) calculations are carried out to study the electronic spectrum of TIX (X = As, Sb, Bi) molecules. Potential energy curves and spectroscopic constants of lowlying electronic states of these isomers have been computed. Dissociation energies of ground-state molecules are calculated and compared with the experimentally determined values. Effects of the spin-orbit coupling on the spectroscopic properties are studied. The zero-field splitting of the ground state of TIX has been estimated from the spin-orbit Cl results. The heavier molecule, TIBi, has a stronger effect of the spin-orbit coupling. Many avoided crossings in the potential curves of Q states of these isomers are reported. Dipole moments of the ground and lowest few bound states, such as (3)Pi, 'Sigma(+), (1)Delta, and (1)Pi, of TIX have been calculated. Transition probabilities of dipole-allowed and spin-forbidden transitions of these molecules are computed. The radiative lifetimes of some of the excited 0(+) states are also estimated.