Translations from the Dodnash Priory Charters under Brantham (Taxatio, 129) include following references to a castle: 'in closely datable document only until 1202 (71-2).... and not long afterwards William (son of) Helte gave land adjacent to the small castle (castello) of Hamo Petit (77)' and '(77) grant in pure and perpetual alms by William son of Helte to the canons, for saluation of his soul and those of his father..... of that part of his land at Brantham above "Aldefeld", which abuts on the castle (castello) of Hamo-Petit. Early C13'. (Suffolk HER ref. Harper-Bill)
Since this seems to be a use of the term castello to mean a manorial centre the most likely location must be that of Brantham Hall, which is earlier than C15 in origin and which was originally moated. I expect in 1202 this was a timber building. However this is by no means a certain identification and the nearby Brantham Court (TM127343) has a name suggestive of a manorial centre although some distance from the parish church. Harper Bill footnotes (p. 17n66) that 'there were four manors in Brantham, One of these came to be known as Brantham Hall, another as Braham Hall, near the hamlet of Cattawade (Copinger, Manors vi, 22-3)'. Braham Hall, at TM099335, is also moated but seems to be the submanor of Brantham.