Visit Macau from HK and Come back to HK

Dear Sir / Madam,
I am a Sri Lankan Businessman . I have obtained my Hong Kong Legal Business visa and will be travelling to Hong Kong on 20th of June 2016 . I have already confirmed my flight details too . The Hong Kong entry permit I obtained already is Single Entry.

I now decided to visit Macau too in the same trip from Hong Kong for 3 days within my 12 days of Stay with my Hong Kong Legal business friends.
I already have received my invitation letter with the other necessary documents from Macau .

1)Do I need to apply another entry permit to Macau ?
2)As I visit Macau within the same trip , and as i am coming back to Hong Kong again within 3 days , and as I am having a single business entry permit to Hong Kong , is it I need to apply another entry permit to Hong Kong(Double Entry Hong Kong entry permit)?

Please advice me ,
Thank you