Thomas made his debut at the Salzburg Festival in 2012 as Papageno in "Das Labyrinth" by Peter von Winter with the Mozarteum Orchestra Salzburg under the direction of Ivor Bolton.

The highlights of his career include Harlequin in Strauss' "Ariadne auf Naxos" under Franz Welser Möst at La Scala in Milan and in a production by Robert Carsen at the Bavarian State Opera. He made his debut as Ford in Verdi's "Falstaff" under Donato Renzetti at the Teatro Lirico di Cagliari and appeared in the world premiere of Mauricio Sotelo's "El Público" under the direction of Pablo Heras-Casado at the Teatro Real in Madrid. Thomas was invited to sing Collatinus in Britten's "The Rape of Lucretia" at the Maggio Musicale Fiorentino, Nick Shadow in Stravinsky's "The Rake ́s Progress" in Rennes and Nantes and Don Fernando in Beethoven's "Fidelio" at the Auditorio Nacional de Música in Madrid. Most recently, he sang as the baritone soloist in Maurice Béjart's ballet "Lieder eines fahrenden Gesellen", by Gustav Mahler, at the Opera Bastille in Paris.

As a sought-after concert and oratorio singer, Thomas Tatzl sang Haydn's "Creation" under Riccardo Muti in Ravenna and also appeared in the production of La Fura dels Baus both at the Lincoln Center in New York and at La Seine Musicale in Paris.

Under the baton of Daniele Gatti, he sang Bach's cantata BWV 78 "Jesu, der du meine Seele" for the Maggio Musicale Fiorentino in Florence. He appeared in the St. Matthew Passion under Philippe Herreweghe and his Collegium Vocale Gent for deSingel in Antwerp and under Alessandro De Marchi at the Theater Basel.

Thomas was the bass soloist in Beethoven's Symphony No. 9 in Milan, Zurich and Madrid and also sang under Antonio Pappano in Rome and Caserta. Under the baton of Maestro Pappano he also sang the baritone part in Brahms' Ein Deutsches Requiem at the Accademia Nazionale di Santa Cecilia in Rome, followed by performances of this work under Matthew Halls in Antwerp and Ghent. He was heard in Mozart's Requiem under Laurence Equilbey and the Mozarteum Orchestra in Salzburg and in Fauré's Requiem with the Netherlands Radio Philharmonic Orchestra conducted by James Gaffigan at the Concertgebouw Amsterdam.

He also performed Schubert's Mass in E flat major accompanied by the Munich Chamber Orchestra and the RIAS Chamber Choir both in the Prinzregententheater in Munich and in the Berlin Philharmonie, Beethoven's Missa Solemnis in Tokyo under the direction of Ingo Metzmacher with the Japan Philharmonic Orchestra and the Mass in C major by the same composer with the Arnold Schönberg Choir in Antwerp's deSingel.

Tatzl is also particularly well known for his impressive performances of German lieder. After his debut at La Scala in Milan with Schubert's "Winterreise", he later presented this song cycle with the Ballet Preljocaj for the Aix-en-Provence Festival, the Gran Teatre del Liceu in Barcelona and the Théâtre des Champs-Elysées in Paris.

He has given recitals at the Schubertiade in Hohenems, the Schleswig- Holstein Music Festival and the Gstaad Menuhin Festival, among other prestigious festivals and venues. He sang Mahler's "Das klagende Lied" with James Conlon and the Orchestra Sinfonica Nazionale della RAI and performed some of Schubert's songs with the Munich Symphony Orchestra at the Prinzregententheater in Munich.

In the 2023/2024 season, Thomas will sing the role of Dr. Falke in J. Strauss' "Die Fledermaus" at the New National Theatre in Tokyo, at the Opéra de Toulon, and will also return to the Opéra de Rennes and the Angers-Nantes Opéra in the same role. He will also sing Bach's "St. Matthew Passion" in Hamburg.