Your address should be on the right and don't put your name there- your name comes at the end, under your signature, so it's unnecessary.
my The Moonlight Restaurant premise- I'd say my restaurant, The Moonlihght Restaurant, (and delete 'premise)
For your information, my Ampang Jaya premise of The Moonlight Restaurant has been set up in and operating since December 2002.- FYI sounds too aggressive. Do you have more than one restaurant? If not, delete the first part. Delete 'set up and'
The business has been doing well for the past few years but has undergone a drastic slump ever since the construction work started this January.- shouldn't you have a coma in here?
hygieneissue- spacing and I'd use the plural
potholed since- either say since when or delete it
beautification trees- wrong word
have even complaint- use the verb not the noun
Hereby I sincerely appeal so- word order and one word needs to be deleted
Thank you- seems to informal