Thermal modification is a property improvement technique that uses high temperatures to treat wood. For wooden structural members used in construction, in addition to the mechanical properties of thermally modified wood, the wood adhesive bond strength becomes increasingly significant. The present study examined the effects of thermal modification, using various temperatures (180 °C, 190 °C, 210 °C, and 220 °C) on the mechanical properties and adhesive bond performance of rubberwood compared to unmodified rubberwood. The results indicated that increasing the modification temperature negatively affected the mechanical properties of the rubberwood and decreased the wood adhesive bond strength. To improve the durability performance and joint strength reduction, a wood/polyvinyl chloride (WPVC) composite material was combined with thermally modified rubberwood at a temperature of 180 °C, which offered the optimum results in terms of the mechanical properties and wood adhesive bond strength of the various proposed modification temperatures. The study also investigated the mechanical properties of hybrid glulam beams made from thermally modified rubberwood and WPVC composites using static flexural tests, comparing the results to those for the thermally modified rubberwood glulam beams. The findings suggested that the modulus of elasticity of the hybrid glulam beams was not significantly affected because the WPVC composite members were placed in a low load-bearing location. The hybrid glulam beams provided a 38.66 % lower flexural strength than the thermally modified rubberwood glulam beams. Overall, the increase in temperature during the modification process negatively impacted the mechanical properties and wood adhesive bond strength of rubberwood. Moreover, a theoretical analysis was carried out to provide a comparison with the experimental investigation by focusing on the flexural behaviour of glulam beams. The analytical model results showed a good correlation with the observed behaviour of the glulam beams produced by thermal modification at different temperatures. In particular, the behaviour of the glulam beams produced by thermal modification at a temperature of 180 °C could be effectively predicted with high confidence.