Flexibility and hardness are very important for expressing color in textile materials using UV curing technology. In the preceding study, the lack of hardness resulted in dye migration challenges. In this study, we investigated the effects of an oligomer, hardener content ratios, and curing time on the UV and thermal dual curable resin on thermoplastic copolyester (TPEE) mono-filament while maintaining flexibility. We observed that an O-3 oligomer with 13,000 mPa·s viscosity, 11.25:4.65 ratio of HDI/Photoinitiator, photocuring time of 40 s, and thermal curing time of 5 min, showed the best formula conditions. By dual curable resin treatment of the TPEE filament, the tensile strength increased under all UV and heat treatments, but the elongation increased after 10 min of heat treatment. We also observed the surface and cross-section of the dual curing TPEE mono-filament.