Král began his motorsport career in karting back in 1998, and during the following seven years he achieved notable success, winning the Czech Republic ICA Junior title in 2003 and the Czech ICA 100 Championship the following year, as well as numerous other titles. In 2005, Král made his Formula Racing debut, finishing third in the Czech Formula 1400 series.
In 2006, Král made the step up to Formula BMW, competing in the GermanADAC series. Driving for Micánek Motorsport, he scored forty points during the year to be classified in twelfth place. At the end of the year, Král switched to Josef Kaufmann Racing to contest the Formula BMW World Final, held in Valencia. He originally finished as runner-up to team-mate Christian Vietoris, but was subsequently disqualified from the race. Král continued in Formula BMW for 2007, this time switching to the UK series with Räikkönen Robertson Racing. He scored a total of thirteen podium places in eighteen races, including six wins, to finish as runner-up to SwedeMarcus Ericsson. He also took part in two Formula BMW ADAC races, taking a single podium position. Král once again took part in the end-of-season Formula BMW World Final in Valencia, this time driving for Mücke Motorsport. Again, he finished second on the road behind team-mate Philipp Eng, but was disqualified for a technical infringement.
In 2008, Král joined Team JVA to contest the InternationalFormula Master series. He finished the season in sixth place, taking three podium places, including a debut win at Oschersleben. He remained in the championship for 2009, this time switching to Italian team JD Motorsport. After taking podium places in Valencia, Brno and Brands Hatch, Král won his first race of the season at the Hungaroring, which acted as a support race for the 2009 Hungarian Grand Prix. He added another win at Oschersleben en route to third in the championship.
In October 2009, Král made his debut in a GP2 car, testing for both Ocean Racing Technology and Piquet GP at Jerez in Spain. Later the same month, he signed with British team Super Nova Racing to contest the 2009–10 GP2 Asia Series. This relationship continued into the main series in 2010, when Král teamed up with his former Formula BMW rival Ericsson. During the sprint race at Valencia, Král's car was launched into the air after he collided with Rodolfo González, before landing heavily and hitting the tyre barriers. Král sustained two fractured vertebrae as a result, and was replaced by Luca Filippi until he recovered. After missing ten races, Král returned to action at the final round of the championship, where he scored his first series points. Král moved to the Arden International team for 2011, partnered by 2010 FIA Formula Two Championship runner-up Jolyon Palmer. He finished tenth in the Asia series. In the main series, he scored his first podium in the Monaco sprint race. Another podium finish at Spa-Francorchamps saw him improve to 15th place in the championship. He moved to reigning teams' champion, Addax, for the 2012 season, alongside Johnny Cecotto, but was replaced by Dani Clos after the first round of the championship. He then returned to the seat for the fourth round of the series. After a run of pointless weekends, he took his first series victory in the sprint race at Spa-Francorchamps, only to be dropped for the following round of the championship in favour of Jake Rosenzweig. He finished 17th in the championship.
