On 2 June 1925, Thung was appointed ‘deputy phytopathologist’ at the Quanjer’s laboratory. He became ‘assistant’ for a year, an appointment which would be extended several times.

Thung’s very first scientific publication appeared in 1926 in the Tijdschrift over Plantenziekten (Journal of Phytopathology) (Issue 32, pp. 161-179), under the title ‘Opmerkingen over Peronospora parasitica op kool’ (‘Observations on Peronospora Parasitica on Cabbage’). Peronospora is a fungal disease.