We investigate the electrical and thermal transport coefficients of an emergent transition metal tri-chalcogenide, namely, TiS3. We implement an accurate description of the electron-phonon coupling and thus of the energy dependence of the relaxation time, which goes beyond the commonly used approximations. We find that standard calculation methods fail in accurately describing the thermoelectric transport properties of TiS3 and one needs to go beyond standard approximations to correctly investigate the thermoelectric performance of TiS3 and other 2D materials. By applying state-of-the-art ab initio methods, we conclude that TiS3 stands as a potential candidate for thermoelectric applications.