Skip CM, split evenly between Bkk and HK. Both offer good sights, excellent food and depending on your budget, some decent shopping. Bkk hotels are much cheaper, HK is on scale of SQ. You can do day trips outside of each city, eg. Bridge over River Kwai full tour trip, old Bkk capital Aryudetta, half/one day trip to Macau, etc.

If you go directly to Thailand and HK threads, much more detail information and suggestions. Both cities, IMHO are much more enjoyable than Singapore.

Weather wise, Thailand is best btw Nov to Feb, HK Nov-Jan but Feb is acceptable (not hot, just might be chilly by Asian standards).