I always take my Kawasaki Z300 to official dealer ship. I don't want some local Somchai trying his village wisdom hotfixes on it. I also want all parts to be original. So if I was you I would take it to official Kawasaki dealership. You are also guaranteed that when the motorcycle comes out of shop it will be fixed. Instead of trying to throw random Chinese parts at it as Somchai recommends.
Once my bike was completely dead. Wouldn;t even turn over. Toke it to the Kawasaki and paid like 1200 baht for oil change and filter and 500 Baht for new starting relay. Yeah, Somchai would do it cheaper, but it's not like Kawasaki gonna bankrupt you.