Hexham was placed as a page in his early youth to Sir Francis Vere, with whom he remained through the siege of Ostend in 1601.
Hexham seems to have served Sir Francis until his return to England in 1606, then remained in the Low Countries, possibly in a town garrisoned by the English.
In 1611 he published a Dutch translation of The Highway to Heaven, by Thomas Tuke entitled De Konincklicke wech tot den Hemel... (Dordrecht).
After Vere's death, Hexham became quartermaster to the regiment of George Goring, with whom he served at the siege of Breda in 1637.
Published in two volumes in Amsterdam in 1636–1637, it contains many maps and coloured plates and counts as the standard Mercator edition.
Another important work was his Copious English and Nether-duytch Dictionarie … as also a compendious grammar for the instruction of the learner.
The English-Dutch part appeared in Rotterdam in 1648. dedicated to Hexham's friend Sir Bartholomew van Vouw, knight.