Thebom made her European debut in 1950 as Dalila at the Royal Swedish Opera (RSO). She returned to the RSO several times, singing such roles as Amneris, Eboli and — in what The Times described as "a not especially successful attempt at a soprano role" — as Elisabeth in Tannhäuser.
Thebom's first appearance on the European stage took place in 1950 as Dalila at the Royal Swedish Opera (RSO). She returned to the RSO several times, performing roles like Amneris, Eboli and — The Times described her attempt at singing Elisabeth in Tannhäuser as unsuccessful.