In Croatia, Thesz families are Croats (from Osijek ).
Prevalence
Only a few people with faimily name Thesz live in Croatia today, in three households only. There were 0 of them in the middle of the past century, and their number remains constant. They are located in one Croatian city only, in Osijek (<5).
Outside Croatia
Family name Thesz is present in 8 countries on four continents. The family name "Thesz " is used by some 300 people in Hungary , small number in the United States , and small number of people in Argentina.