TheVietnamese, who stood second in the qualifying round, triumphed onSaturday in the women's vault event with her result of 14,525 points.Giulia Steingruber of Switzerland came second (14,413) and Teja Belakfrom Slovennia was third (14,350).
It is her second title in almost a week.
Earlier, Thanh topped the same event at the Artistic&RhythmicGymnastics World Top Competition in Incheon , South Korea.
The World Cup winner will later take part in the all-round and parallel events.
In Osijek , Thanh's teammate Pham Phuoc Hung claimed a silver medalin the men's parallel category. Hung won 15,625 points to bag thesecond place, a big jump compared to the sixth position he scored duringqualification rounds.
Slovenia 's Mitja Petkosek who took15,725 points won a gold medal while Oleg Stepko of Azerbaijan camethird with 15,325.
Another Vietnamese, Dang Nam, will later compete in the men's rings.
The Vietnam team is participating in the tournament with fiveathletes. They are also members of the squad that will compete at thecoming 18th Asian Games in Incheon , South Korea , in September.-VNA