Hand extension is crucial for stroke survivors with spasticity, where their fingers become rigid and their thumb remains curled within the palm. Due to the underactuated nature of the hand, the dominance of flexor muscles over extensors, and the limited surface area available, developing an extension glove with thumb assistance poses a challenge for researchers. This paper introduces a fully wearable soft hand extension glove based on the X-pouch and strap system, addressing the above challenges. The glove enables adequate finger extension, thumb abduction, and extension for high MAS score patients. Modelling and testing revealed extension torques of up to 2.7 Nm at the MCP joint and 0.67 Nm at the PIP and DIP joints. Performance evaluation, including comparison with existing methods, demonstrated the glove’s superior extension capabilities using a model hand with realistic stiffness. Furthermore, the glove’s effectiveness was confirmed through testing on a stroke patient with MAS = 2, validating its on-body functionality.