If you installed the new version of Kmplayer (3.9). Without any disable option, you should see a advertisement (ads) slide panel in right side & even in the full screen view.
Although they said this player is free, It seems likes developers of the Kmplayer are going to make some money now. this is called “Adware”.
This ads panel appears only when you connected to the internet. So if you want to to remove / disable advertising sidebar in Kmplayer you should disable internet accessing by the Kmplayer software.
to disable internet access by kmplayer.
In Windows computers,
Method 1 (easy)
Go to internet explorer -> Internet options -> (on Internet Properties window) Security tab ->click on Restricted site -> click (button below) sites -> add this URL on that box player.kmpmedia.net
Method 2 (for Pros)
Open ‘host’ file in windows
Using one of above methods you can prevent the kmplayer to connect to the internet and no sidebar will appear!