Spin-orbit coupling effects in the ground state and four low-lying excited valence states a1Δ, B3Σ−, 13Δ and 13Σ+ of SeS molecule

► Convergent behavior is observed with respect to the basis set and level of theory. ► PECs of five Λ-S and 10 Ω states are calculated. ► Spectroscopic parameters of five Λ-S and 10 Ω states are obtained. ► Effect on the PECs by core-valence correlation and relativistic corrections is discussed. ► Calculated spectroscopic parameters achieve high quality.