His professional career began at TSV 1860 München in the 2nd Bundesliga. He scored eleven goals in 35 games there. From 1982 to 1990 Waas played for Bayer 04 Leverkusen, then at Bologna FC, Hamburger SV, FC Zurich and at Dynamo Dresden. He scored 74 goals in 247 league games, in Switzerland 19 results. Between 1983 and 1988 he came to eleven national missions, where he scored a goal. For the Olympic national team, he played his only game against Israel in 1983 and the 2-0 score a goal.
In 1988, he won the UEFA Cup with Bayer 04 Leverkusen. In the final second-leg match against Espanyol, he was the decisive penalty shootout to the scorers.