I travel to Asia a few times a year, and I find that buying early doesn't really cost me anything less. Try messing around with a ticket search engine like
Kayak to see what kind of results you get.
You'll save some money by not traveling on Friday-Sunday. It's generally like Tuesday and Wednesday will save you a little.
Buying from the airline Web sites seems to be the best deal if you're buying online. The other route which will save you a lot if you can find something is to go through an Asian travel agency. When I say "Asian", I mean Chinese in my case but I'm guessing there must be Korean ones too... or maybe the Chinese travel agents sell tickets to Korea?? I don't know.
Anyway, I think the deal with the Asian travel agents is that they get together and buy up a block of seats and then sell then as a group rate. These tickets
are less expensive but I've not had a lot of luck getting them. They're usually gone for the dates I want and the tickets are very restrictive. That is, they often won't get you any award miles, they're not changeable, they're not refundable, etc.
You can find the Asian travel agents listed in the travel sections of large city newspapers, or I can post the Chinese ones that I've tried in the past...
Good luck.