After a long karting career, Theobald stepped up to single-seaters in 2002, racing in the Formula König series in his native Germany.

He finished the season just outside the championship's top ten in eleventh place, with the highlight being a fastest lap at the penultimate round at the Lausitzring.

[4] After testing for Pons Racing at the end of 2006, Theobald made his Formula Renault 3.5 Series debut at Donington Park in September 2007, replacing Jaap van Lagen at Eurointernational.

[6] Theobald made a return to the series in 2008, signing for British team Fortec Motorsport a few days before the opening round of the season at Monza.

[7] He completed the first four races of the season for the team at Monza and Spa-Francorchamps before being replaced by Fairuz Fauzy from the Monaco round onwards.