Short rotation teak wood has been produced to overcome the scarcity of long rotation teak. The short rotation teak has low quality, especially in dimensional stability and durability. Glycerol-maleic anhydride (GMA) treatment as non-biocidal wood preservation system was applied to improve technological properties, especially dimensional stability and durability. Impregnation with 10% w/w aqueous solution of GMA followed by thermal modification at 150 and 220 °C under inert conditions was investigated on short rotation teak sapwood. The following technological properties were studied: chemical compound; mass alteration; density; leachability; dimensional stability (volumetric swelling, anti-swelling efficiency (ASE), and water uptake; modulus of elasticity; modulus of rupture; decay resistance; and termite resistance. The results show that chemical modification with 10% GMA combined with thermal modification increased ASE by 62.31% and 73.22% for 150 and 220 °C, respectively, indicating improved dimensional stability. Decay resistances of GMA-thermal treated teak wood against fungal decay of Coriolus versicolor, Pycnoporus sanguineus, and Coniophora puteana were categorized to be class 1 (very durable). Weight loss of GMA-thermal at 220 °C against termite attacks was 0.19%, which presented excellent durability (rating 10) against subterranean termites. Fourier transform infrared and carbon 13 nuclear magnetic resonance analyses indicate that the presence of reaction between GMA polymer with lignin occurred after thermal treatment at 220 °C. Thermogravimetric analysis shows that GMA-thermal treatment also presented better thermal stability than untreated wood. GMA-thermal treatment gave a significant improvement in dimensional stability and resistance to wood-decaying fungi and termite.