Training first as a mechanic, he later acquired the Swiss federal maturity degree and pursued academic studies whilst in employment.
He worked in research from 1970 to 1977 for the British pharmaceutical group Beecham, mainly at their Swiss laboratories, but also at the pharmacological institute of Gothenburg, Sweden.
The new ETA, with 2,200 employees, gradually introduced more advanced technology in the manufacturing of quartz movements and full automation throughout its production.
In this period, the company integrated all of the Ebauches factories into ETA SA, and regained the brands Omega, Longines and Tissot.
Between 1992 and 1995, Thomke was CEO of Motor-Columbus AG, refocusing its activity on the primary energy sector under the new name of ATEL, with a mandate from the majority shareholder, the Union Bank of Switzerland (now known as UBS).
In addition he worked until 1997 for the Oerlikon-Bührle Holding Company (OBH), as Chairman and CEO between 1991 and 1997 of both Pilatus AG-Flugzeugwerke and Bally International AG.