His biography listed him as a graduate of the Vulcan Academy of Sciences. He was a top student in every class, including graduate-level classes in computer technology taught by Sarek of Vulcan. These gave him excellent computer infiltration skills. He had a tricorder in his inventory.
Circa 2358, Darryl Adin and Tasha Yar considered a tactical exercise in which they had to seize a hill guarded by seventeen Mercaptans using only three security personnel, including Thonis. Adin suggested using Thonis to disrupt their Troop Controller's orders. (TNG novel: Survivors)