Hey buddy. It is bad to hear that you are having some grief. I recall replying to you when you were considering buying this bike. Did you spend the few hundred baht getting the valve shim clearances checked/ You asked what the danger with these bikes were and that is it.
Not trying to tell you so but you need to get on top of this.
Now with the oil, if you are losing that much oil in such a short space of time. It can only go to three locations:
1. Into the combustion chamber and burnt. That much oil will have blue smoke out of the exhaust from engine start and only get worse when riding. The tip of the exhuaust will be black and possibly dripping black crud.
2. removal by gravity: there will be pools of oil somewhere.
3. And the one you allude to which is oil in the cooling system. Take off the radiator cap and you will see some film of oil. That much oil would have your radiator catch flow bucket full and overloaded. If the head gasket is leaking into the combustion chamber then the oil and the water will be getting burnt. And I dare say you would have siezed the engine by now.
As a couple of people already asked, did you check oil with the bike level and vertical? You said yes. Check again because none of what you are saying would give minor symptoms to your bike. Something here is not adding up.
Also, it does not take much for labour art the Kawa shop. They are specialists. Get them to diagniose.. Just go in and ask them what is wrong. Do not give your opinion. Price usually goes up when people like to assist diagnosis.
Again, I will state here, something if not adding up. You are either not telling the whole story or you are playing with us,. Thast much oil just does not disappear without a strong trail.