Sorry to break this to you, but your motorcycle engine has for some reason suffered significant internal damage and needs the attention of an experienced mechanic. Black smoke means that engine oil found it's way into combustion chamber. The problem can be as simple as a blown out gasket, but it could also mean a broken piston ring, so lets hope that it's something simple...
Hmm. Is the engine running basically OK? If not it might simply be the air filter is plugged, of the choke is stuck open and the bike is running very rich.
Does exhaust smell of petrol or burnt oil?
Rules of thumb.
# 1 Black-ish smoke is oil, white smoke is coolant.
#2 black-ish smoke on acceleration is piston blow by. Smoke on overrun is worn valve guides.
Check the air filter , choke circuit etc first. if bike is FI then this might be academic but worth a look.
Then see if the smoke occurs on acceleration or overrun. This won't change the fact that it needs to be stripped down but at least it will let you know what is wrong when someone explains how they are going to fix it.
Outside chance you may just have a stuck piston ring which maybe loosened with some Sea Foam. DIY instruction for making a close substitute may be found on the interweb.
Can't find the ingredients, not technically inclined, you live in BKK and can carry beer you can come round and we'll go shopping nearby and play mad scientist together.