After the death of Thomas’s father Robert Hethe in 1396, the abbot of Bury St. Edmunds, as overlord of some of his property, granted Thomas’s wardship and marriage to his mother, Margery; but the Crown also had an interest in the Hethe estates and on 15 Nov. 1399 Henry IV gave custody of the inheritance to one of his retainers, John Reymes. Subsequently, young Thomas married one of his guardian’s daughters. In 1403 it was alleged that some land in Barway in Cambridgeshire which should have pertained to the Crown during Hethe’s minority had been illegally concealed. The bulk of his landed holdings were in Suffolk, however, and included manors at Little Saxham and Denham, as well as property at Risby, Mildenhall, Westley and Fornham All Saints.
Hethe evidently preferred the life of a country gentleman to the career of a busy lawyer which had occupied his father, and for the most part records of him are related to dealings with family or strictly local affairs. In 1405 he stood surety in Chancery for his uncle, Thomas Hethe of Mildenhall, who was then engaged in a lawsuit; and in 1414 he and the older Thomas both acted as trustees of property belonging to another uncle, Richard Hethe, and his wife Elizabeth.
When Hethe was elected to his only known Parliament in 1420, his uncle Richard stood surety for his attendance; and both uncle and nephew were mainpernors for William Rookwood on the occasion of his election for Suffolk to the next Parliament, that of 1421 (May). Nine years later Thomas Hethe was to be present when his uncle’s widow took the veil at a ceremony in which Abbot Curteys of Bury St. Edmunds officiated. His relations with Curteys’s predecessor, Abbot Excestre, had not been so cordial: in 1424 a quarrel had flared up between them, and the abbot had been required to enter into recognizances of £2,000 with the Crown as surety that he and the monks at Bury would do Hethe no harm. By contrast, Hethe was on good terms with several members of the gentry of East Anglia: for instance, in the 1430s he served as a feoffee of the manor of Little Dunham, Norfolk, on behalf of Sir Guy Corbet, and in 1435, at the Suffolk elections to Parliament, his name was put down as a mainpernor for Henry Drury.
Hethe had also made a good match for his only daughter, Elizabeth (d.1464), who four or more years earlier had been wedded to William, grandson and heir of the wealthy soldier Sir William Bardwell. Hethe died at the age of 56 on 7 Nov. 1439. By his will, dated the preceding day at Bardwell, where his daughter lived, he requested burial in the parish church at Hengrave and named Anne his wife as principal executor. The disposal of his estates had been arranged on 30 Oct., Hethe stipulating that Anne was to hold them for life, paying £10 a year out of Little Saxham to Elizabeth. Both women were ‘big with child’, and Hethe ordered that if a male heir should result from either pregnancy the son or grandson should eventually succeed to his estates. Should there be no such male issue, Elizabeth was to have the lands for life after Anne’s death, and then they were to be sold. In the event, neither produced a son, and following the death of William Bardwell in 1440 the reversion of the manor of Hengrave and other of Hethe’s properties was sold to Humphrey, duke of Buckingham, for 220 marks.