Ecclesiastic and diplomat. Educated at Salamanca, Spain, ordained and appointed chaplain to the Spanish embassy at London, England in 1767. Twenty-five years later, when Spain and France severed relations with England, Thomas took care of the Spanish interests in England. He was subsequently entrusted by the British with diplomatic missions in Madrid, Spain, and in Ireland. In 1795 he was appointed first president of Maynooth College, and shortly after was consecrated Bishop of Waterford and Lismore, Ireland.