Answer from Arab Emirates Samsung
Generally, I would refer you to your country's customer service, but instead this time they came to me, so here is the answer they provided:
The short of it is that the WIS12ABGNX will not work on your TV.
Your model (UA40D5000PR) is a Middle Eastearn model, and according to the user's manual, it apparently only supports three wireless LAN adapters: WIS09ABGN, WIS09ABGN2 and WIS10ABGN. But the WIS12ABGNX is not supported by your TV. (User's manual: http://downloadcenter.samsung.com/content/UM/201201/20120128143536163/UX5DVBAS1A_UX9DVBAS1A-ENG-1018.pdf )
Also, when you check SamsungParts.com, you're checking American models, not Middle Eastern. So it won't be the same model. But you were correct that on the Arab Emirates Samsung portal, the model was not listed, so it's being corrected for other users.
Hope that helps!
-- HD Tech