Offices in Korea are notoriously HOT and stuffy. If you're in a car btw hotel and meeting venues, you don't even need a heavy coat, even in the coldest weather [at least in Seoul]. I've done Korea [cold] and then SE Asia [hot/humid] from Nov to March for decades, and can still get by with just carry-on.

If you're still concerned, pack lightweight suits and add layer of silk undies...seriously ^