How to get back passport for another trip during visa application being processed

Hi,

I am Vietnamese and processing Hong Kong visa application for a business trip from 13th to 15th Nov 2019.
During my visa application being processed, I have a business trip to France from 14th Oct to 2nd Nov 2019, therefore I will certainly need my passport.
Do I need to send my original passport to Hong Kong Immigration Department? If so, how can I get my passport back for my France trip on 14th Oct 2019 during the application processing time?
I would appreciate your advice. Thanks very much