Charlton was born near Wellington, Shropshire, younger son of Robert de Charleton of Apley, a small landowner.
Thomas' eldest brother was John Charleton, 1st Baron Cherleton, who became a statesman of some importance.
Both brothers were in the household of Edward II, and Thomas received numerous ecclesiastical preferments.
His mission does not seem to have been a success, as most of the existing judges, notably the notoriously corrupt Simon Fitz-Richard, the Chief Justice of the Irish Common Pleas, fought off all attempts to replace them.
John resigned as justiciar in 1338, following a dispute, and Thomas moved from the Chancellorship to the position of custos rotulorum for Ireland.