This paper introduces an unconventional constitutive model for soils which deals with a unified thermo-mechanical modelling for unsaturated soils. The relevant temperature and suction effects are studied in light of elasto-plasticity. A generalized effective stress framework is adopted, which includes a number of intrinsic thermo-hydro-mechanical connections, to represent the stress state in the soil. Two coupled constitutive aspects are used to fully describe the non-isothermal behaviour. The mechanical constitutive part is built on concepts of bounding surface theory and multi-mechanisms plasticity, while water retention characteristics are described using elasto-plasticity to reproduce the hysteretic response and the effect of temperature and dry density on retention properties. The theoretical formulation is supported by comparisons with experimental results on two compacted clays.