Born in Czerniki, East Prussia, as Sohn eines evangelischen Pfarrers studierte Thomaschek an der Albertus-Universität Königsberg Theologie und Philologie.
[1] Won for singing by Eduard Mantius in 1847, he was trained by Franz Hauser in Munich.
(1850/51), Barfüsserkloster Zurich (1851/52), Volkstheater Rostock (1852/53), Staatstheater Kassel (1853/54), Deutsche Oper Amsterdam (1854/55), Theater Görlitz [de] (1855/56) and Szczecin City Theatre (1856/57).
After he had worked in 1864/65 at Stralsund Theatre had been a singer and director, he went even further north in 1865/66, to the new (German) Latvian National Opera.
He spent his 23 years as a widower in a home for needy stage artists, which Marie Seebach had donated in Weimar in her will.