A pupil of the Neapolitan tenor Fernando De Lucia (1860-1925), Thill made his opera debut at the Paris Opéra in 1924, and continued to perform there and at the Opéra-Comique for several decades. He also sang throughout Europe and in South American, proving highly successful at La Scala, the Rome Opera, the Verona Arena, the Vienna State Opera, the Teatro Colón and the Royal Opera House, Covent Garden. He sang 14 performances of seven roles over two seasons (1931-1932) at the Metropolitan Opera in New York, but he had difficulty settling in and was less well received by American audiences.
Thill made many 78-rpm discs of French, Italian and German operatic arias and recorded a complete performance of Massenet's Werther for French Columbia in 1931. These records are freely available on CD transfers. The best of them display the gleaming tone of his voice in its prime, as well as demonstrating his exemplary taste. Thill also appeared in several French films.