Hauser started his youth football with local team Sportclub Schopfheim, playing there until he left school. In 1980, he transferred to FC Basel and played in their youth team in the highest level of youth football in Switzerland. In 1981 Basel became Swiss youth champions and Hauser was the league top goal scorer.
Aged just 17 years, Hauser trained and played regularly in Basel's first team. Between 1982 and 1988 he scored over 30 goals for his team in the Swiss Nationalliga A and the Swiss Cup. In 1983, he won the Uhrencup with Basel, scoring a goal in the semi final match against FC Grenchen. After a turbulent time with a financially troubled FC Basel, and following the club's relegation to the Nationalliga B at the end of the 1987–88 season, Hauser transferred to local rivals BSC Old Boys. He played with them for six months before transferring to Sunderland during the winter break.
Hauser made his debut for Sunderland coming on as a substitute for Marco Gabbiadini in a 2–0 League win at Roker Park against Hull City on 25 February 1989 in front of a crowd of 14,719, following a £200,000 transfer from BSC Old Boys. He went on to make four further substitute appearances until making his full debut against Chelsea F.C. in a 2–1 loss on 21 March 1989. Hauser's first goal came at Boundary Park in a 2–2 draw with Oldham Athletic, he scored one week later in a 2–1 victory against Shrewsbury Town at Roker Park.
In Sunderland's 1989–90 promotion season Hauser scored six goals including both goals in a crucial 2–1 win against Brighton and Hove Albion on 24 February 1990 at Roker Park. In scoring the equaliser in a 2–2 draw at Roker Park against Port Vale F.C. on 30 December 1989 and only six minutes after coming off the bench against Hull City at Boothferry Park on New Years Day 1990, Hauser can lay claim to having scored Sunderland#s last goal of the 80's and first goal of the 90's. Later that season Hauser went on to feature for Sunderland in the play-off final at Wembley Stadium coming on as a substitute for Eric Gates in front of a crowd of 72,873 on 28 May 1990. When Hauser replaced Gates he became the first non-British born player to represent Sunderland at Wembley.
The 1990–91 season was Hauser's only in the top flight of English football, he made 10 appearances finding the net only once against Southampton F.C. at The Dell in a 3–1 defeat.
After Sunderland's relegation back to Division 2 Hauser started the season promisingly. Although not included in the squad for the opening league game, he did start the next five, the last of those five being a 1–1 draw with Blackburn Rovers at Roker Park which would prove to be Hauser's last league start for Sunderland. His final start, and indeed goal for Sunderland came in the League Cup in a 2–1 defeat at home to Huddersfield Town in front of only 8,161. Hauser's final appearance for Sunderland came on Boxing Day 1991 replacing Paul Hardyman in a 1–0 defeat to Tranmere Rovers at Prenton Park.
Thomas remains a cult hero amongst the Sunderland fans who saw him battling with opposition defences at Roker Park, and is known as "The German Sub" after coming from the bench for 39 of his 65 appearances.*1 appearance in FA Cup and 1 in Zenith Data Systems Cup
BaselSwiss Champion at youth level: 1981
Uhrencup Winner: 1983, 1986
SunderlandPromotion to Football League First Division: 1990
Thomas Hauser is married and has one daughter. He spent some time living in the Netherlands working for Celtic Glasgow as a scout. Today he lives in Basel and is youth team trainer together with Louis Crayton (ex-FCB Goalkeeper) for BSC Old Boys.