Details of Nhơn's early life are unknown except that he was a low-ranking naval officer of lord Nguyễn Phúc Thuần.
In the early 1770s, the Tây Sơn revolt broke out and quickly occupied a large part of the Nguyễn Lords’ territory, in the southern half of modern-day Vietnam.
Thereafter, Nhơn conflicted with Lý Tài, an ethnic Chinese mercenary general of the Nguyễn army, and was forced to flee to Bến Tre where he set up a defensive position.
Taking advantage of the more favourable situation, Nguyễn Ánh sent a diplomatic mission to Siam to propose a treaty of friendship.
Nguyễn Ánh sent Đỗ Thanh Nhơn to help the uprising, which saw Ang Non defeated decisively and executed.
[9][10] The reason for this assassination remains unclear, but it was postulated that Nguyễn Ánh did so because Nhon's fame and military success was overshadowing him.