Thien didn't enjoy a good start when losing to his rival 4-6 in the first set. However, the No 1 seed powered to overcome the Danish player 6-1, 6-4 in the next two sets.
He will next play against Lasse Muscheites from Germany.
In the boys' doubles, Thien and his partner Fredrik Prosch Hage from Norway lost to Dutch pair Douwe Disbergen and Bernard Wezeman in the second round.
The tournament will wrap up today.
