Werder Bremen are in talks to take the winger on-loan.
Werder sporting director Frank Baumann confirmed the club's interest and told Weser Kurier: "[Chong] is very fast, he comes in from the wing - he fits our profile.
"We can add two or three more players. Borrowing guys from top clubs like this can make sense to us. Because of our situation, he's a player who could be interesting."