If my training visa ends on 27th, can I extend as tourist for another 4 days and leave HK on 30th?

I am a Filipino who has been accepted for a four-week training in Chinese University of Hongkong under the sponsorship of UBCHEA in the said university. I am currently completing all the documents for the entry permit application. The stay is from May 31-June 27.
My concern is that I am planning to extend my stay in Hong kong till June 30 after my four-week training. From June 27-June 30, I intend to stay in Hongkong to tour around and be a tourist. My specific inquiry is, Since my entry permit is till 27th only, how may I extend my stay even as a tourist? Shall there be a need for me to exit and reenter thru Macau even a day earlier (26th) to avoid illegal stay or extension? Or shall it be possible that I seek permission/consent from Immigration department of the said extension?
What shall I do? Hope you can give me advice on this as I don't want to be caught illegally on this.