The club was founded as Heidebloem Voetbalvereeniging Hulst on 14 June 1942, joining the Royal Belgian Football Association just a few months later. In 1943 the first dressing rooms were built next to the pitch in Hulst, a village encompassed by the municipality of Tessenderlo. In 1970 a new sports centre was built, which was completed in 1973. At that time the club played at the lowest levels of Belgian football, mainly in the third and fourth provincial level in Limburg, at that time corresponding to the seventh and eighth level of Belgian football. In 1992; the club obtained royal patronage for its fiftieth year of existence, thus becoming Koninklijke Heidebloem Voetbalvereeniging Hulst. Two years later it succeeded for the first time to promote to the second provincial level, the sixth level of Belgian football and almost promoted again the following seasons, losing promotion play-offs twice. The club relegated in 1998 and started merger negotiations with two neighbouring clubs within Tessenderlo: VK Penarol Engsbergen from the village Engsbergen and Schoot Sport from the village Schoot. In preparation of the merger, the club became KVV Thes Sport Tessenderlo in 1999, with the acronym Thes standing for Tessenderlo, Hulst, Engsbergen and Schoot. The clubs in the end did not find a mutual agreement and continued to compete separately during the 1999–2000 season. Schoot Sport did not want to cooperate and would eventually cease to exist in 2002. Penarol Engsbergen did cooperate with Thes Sport in the youth leagues, but remained a separate club. In 2001, the club moved from its accommodations in the commune of Hulst to the Gemeentelijk Sportpark closer to the centre of Tessenderlo. The terrain was available because Looi Sport, which was the original occupant, had gone defunct a few years before that in 1997. Meanwhile, Thes Sport started its rise in the ranks of Belgian football, promoting to the first provincial division in 2003 and even into the national leagues in 2005, before relegating back in 2009. In 2015, the club again gained access to the Belgian Fourth Division, the lowest level of national football, at which time the merger with VK Penarol Engsbergen did complete and the latter ceased to exist. Following a title in the 2017–18 Belgian Second Amateur Division, the club promoted for the first time ever to the third level of Belgian football.
