Starting in 1961, he led his own quartet, which over time included Egil Kapstad, Terje Rypdal, Laila Dalseth, Espen Rud, Bjørn Alterhaug and Per Husby.
[5] In 1967 Thingnæs was named best trombonist in the magazine 'Jazznytt musician vote' and in 1969 he led a Norwegian sextet at the prestigious Montreux Jazz Festival.
Together with Philip Kruse, Thingnæs wrote the music for the Norwegian Eurovision Song Contest entries "Hvor er du?"
Other pop music collaborations include Wenche Myhre, Lill Lindfors and Svante Thuresson, as well as production credits for, among others, Bodega Band (1977).
In addition, Thingnæs worked as a conductor at two Oslo theaters, the Forsvarets staff music corps and, for over thirty years, the Kampen Janitsjarorkester.
In the same year, Thingnæs created his "Sonnets to Sundry Notes" of Music for symphony orchestra, big band and choir, based on texts by Shakespeare.