Selective enzyme catalysis is a valuable tool for the processing of monomers into value-added materials. In the present study natural resources were used to retrieve an ω-hydroxy fatty acid monomer containing an epoxide functionality. A procedure was developed for the synthesis of dual-functional oligomers by utilizing lipase catalysis in a one-pot synthesis route. The chemoselectivity of the enzyme allowed addition of thiol monomers to the retrieved epoxy monomers, without harming the epoxides, achieving a thiol–epoxy functional polyester resin. The synthesis reached full conversion (>99%) after 8 h. It was possible to selectively crosslink the resin through UV-initiated cationic polymerization of the epoxides into thiol–functional thermosets. The curing performance was followed in situ by real-time FTIR. The thiol groups on the surface of the film were accessible for post-modification.