Thomas came from a leading Lostwithiel family, two of whose members had sat in the Commons: a Ralph Curteys† represented the borough as early as 1305, and John Curteys, perhaps Thomas’s father, did so in 1363, having earlier served as mayor of Lostwithiel in 1354. Another kinsman, Gerard Curteys, an important tin merchant, had in the 1330s held eight messuages in Lostwithiel as well as land on the nearby manor of Penlyne. Thomas’s putative father, who acted as a juror at inquests held in Cornwall following the death of the Black Prince in 1376, is likely to have been the John Curteys who was murdered near Perranporth in 1381.
In 1373 Thomas and John Curteys were accused at the Launceston assizes of unlawfully disseising Richard Cosyn of his property in Penkneth, a vill which formed part of the town of Lostwithiel. Four years later Thomas stood surety at the Exchequer for the prior of the Benedictine house not far from the town at Tywardreath. By the time of his first return to Parliament in 1383 he had acquired property at Pill, in the nearby parish of Lanlivery, and in August that same year he and his wife obtained a licence from Bishop Brantingham of Exeter to have an oratory there, a privilege which, over 20 years later (June 1405), Bishop Stafford confirmed. Curteys once, in 1384, presented an incumbent to the church at Warleggan. In addition to these holdings, from 1400 onwards he had a reversionary interest in lands belonging to John Archer of Lizard.
Curteys is recorded on various occasions engaged in Cornish affairs: acting as a surety for the peace at the Launceston assizes; making a property evaluation in a dispute between the bishop of Exeter and John Tregorrick†; and appearing, at the assession court of the duchy of Cornwall held in the summer of 1406, as surety for the lessee of the chases and moors at Helston-in-Kerrier.