Haas was a defensive midfielder. During the 1960s, he played 20 times for the Austria national football team. He joined Admira Vienna in 1958, where he stayed for 14 seasons with short intermezzos at Wiener SC and in Switzerland with FC Basel.
After the end of his playing career in 1973, he pursued a career in coaching and law. He managed teams in the Austrian Bundesliga, including First Vienna FC, Admira/Wacker and Grazer AK. He was also the manager of the Austrian national team between 1982 and 1987, and later became a football commentator for the national broadcaster ORF.
Haas has also held important functions within the Austrian Football Association, including that of president.
He is also the author of several books, including:
• 1977: "Sport und Steuerrecht"
• 1991: "Fussball als Beruf: Berufsfeld für Juristen"
• 2002: "Das große Spiel"
• 2004: "Fuaßboi is ned olles"