Tough question as you don't want to look like slime or a perv if you guess incorrectly. Like picking up girls, you will have to ask your wingmen to help out.
I suggest you two go for some after work drinks at Wanchai. Meet up with some of buddies (pre-arranged wingmen) at some of the more respectable bars with a live band such as Amazonia or Dusk to Dawn (places with mixed crowd of civie, tourists, and wgs). After 2 or 3 rounds of drinking, you will had the opportunities to observe how your client looks at the girls in the crowd plus some of your buddies may have 'bonded' with him.
By then you announce to your client that you have to go home early as you have to do a conference call with Europe or States (pick one) before it is too late. Then on cue one of your friends has to speak up and invite your client for further drinking and would be willing to show him more of the nightlife. If done right, your client would agree and go with your friends somewhere else.
If anything happens or not, at least you will be in the clear. Plus you won't look slimy for suggesting some action as it was your dirty friends who were trying to tempt him, not you.
Of course you will have to go home so he doesn't run into you should he does do something. The next day you can innocently ask him how did the night go and ask him if he wants to go for drinks again at night and if he wants to go back to the same place as last night. Then you check out his facial expressions.