Baker, a former England Under-19, came through at Somerset before joining Hampshire over the winter. He was called up for the England Lions tour of Australia, making his first-class debut against Australia A in the final tour match and finishing with figures of 3 for 60.
His performances, which also included a match haul of 5 for 71 against a Cricket Australia XI, caught the eye of Lions head coach, Andrew Flintoff, with the ECB subsequently putting him on contract until September.
“It has been an absolute pleasure to see Sonny thrive over the winter,” Flintoff said. “He and I are very different in character and personality, but it has been a delight to see the pride he takes in wearing the Three Lions, the energy he brings to every ball, and the theatre and magic he creates on the pitch.
“His professionalism and dedication to every aspect of his game are an example to all. Sonny has a bright future ahead, and we look forward to continuing to work with him and Hampshire over the coming years.”