De Munck Sr. worked as a stoker at a gas company in Goes, Zeeland, where he met Johanna Maria Labeur, a widow from Kattendijke.

[3] After a promotional match against Goes, Sittardse Boys offered him an opportunity to move to a higher level as a way out of working at the factory.

As a goalkeeper for Goes, he had excelled in such a way that he could get a paid contract with Sittardse Boys in 1944, as result of a deal with a sponsor at the club, who thereby prevented him from being employed as a forced laborer in Germany.

[6] The move, however, did not materialise after it became known that De Munck had received money while in Sittard, something the Royal Dutch Football Association (KNVB) were fiercely against, as they still adhered strictly to the amateur principle.

He immediately showed his talent after arriving at the club, and "on the [goal-]line and in control of the penalty area [he was] equally strong," which helped the Cologne-based team finished the season with the fewest goals conceded, securing a fourth place.

However, the future German national goalkeeper left the club after twelve months after losing the competition for becoming the starter to De Munck.

FC Köln finished the following seasons with fifth (and again the fewest goals conceded) and second place, before reaching the DFB-Pokal final as well as the in 1954.

[8] In the subsequent European Cup, DOS, with De Munck in goal, were knocked out of the competition in the preliminary round after two losses (3–4; 1–2) to Portuguese club Sporting CP.

In the friendly against France on 23 April 1949, he made his debut as a replacement of regular goalkeeper Piet Kraak, where he was only able to concede a goal to Jean Baratte in the third minute in the 4–1 win.

[10] A year later, De Munck made his comeback for the new professional national team – again against Denmark – and remained the starting goalkeeper until 1960.

He made his last international appearance for Oranje on 24 April 1960, exactly eleven years and one day after his debut, in a 1–2 defeat in Antwerp against Belgium.

As was the case with his difficult international career, the KNVB disallowed him to pursue coaching, as they were of the opinion that De Munck did not have the correct papers.

The KNVB initially did not recognise the validity of his diploma, but was still willing to admit him as a manager after the intervention of Prince Bernhard, with whom he had a friendship.

After his second period at Vitesse, De Munck also coached amateur clubs Minerva and Arnhemse Boys.