Thomas was born in Marseilles, and was a student of Alexis Paccard and Leon Vaudoyer at the École des Beaux-Arts in Paris. He won the first Prix de Rome in 1870, and became the youngest winner of the French Academy in Rome from 15 February 1871 to 31 December 1874. In 1875 he studied the Temple of Apollo at Miletus. His study of the Temple of Athena at Priene earned him a medal at the Exposition Universelle (1878).