 Thynne entered the Queensland civil service, resigned later to take up the study of law, and was admitted as a solicitor in 1873, where he prospered in his profession.In 1882 Thynne was appointed a member of the Queensland Legislative Council.He was Minister for Justice and Attorney-General of Queensland in the second McIlwraith ministry from June to November 1888 and held the same position when the ministry was reconstructed under Morehead until August 1890.