Hong Kong in December/January can be 6 degrees, 95% humidity and with Siberian gales blowing. You might only get a month or six weeks a year out of your tweed jacket, but if you like outdoor activity you will be thankful for it.
The H-range tweeds from Islay Mill are thornproof-style sporting tweeds and can handle abrasion or snagging without incident. Very good for sporting trousers.
The short answer is, use a pattern that you like! Herringbone and houndstooth are pretty uncontroversial patterns and would make a good first suit. Honking loud checks, like the Harris Tweed Tartans, are perhaps best left for when you feel more adventurous.
Some family-owned mills which make excellent, very reasonably priced tweeds without merchants' markups can be viewed below. I have garments made from each of their tweeds and I am very happy with them.
A linen suit was mandatory in that region for the well-dressed gentleman, be he sweaty Caucasian or hypohidriotic Oriental, before air conditioning or electric fans were invented and the best one could hope for was an energetic punkah-wallah or a cool breeze. Tens of thousands of Singaporean professionals wear a suit to work every day, and they seem to survive. Most occasions that call for a suit are indoors, so you should be fine. If you are fit and acclimatised, a...