All 3 clubs have watched the 23-year-old on several occasions and are preparing to swoop for him as RKC lie bottom of De Eredivisie.
The Dutchman's contract runs out in the summer and with interest coming from England's top leagues he looks likely to leave.
"I am willing to stay for a longer period in Waalwijk, however I want to know my future soon," Fung told De Telegraaf.