In Some Ragnarok Clients And Mostly Ragray clients have default setup to keep Poping out Pm Window because of which Chatting becomes harder and its even worst for players who use battlemode.
So here is the Solution for this problem. (click on image if you want full size view)
So if your Pm window keeps coming like this..
Press alt+h and click on friends setup window as shown in image (magnifier image option)
After Selecting Friends Setup Option then 3 option will pop up as shown in the image.
Deselect/Uncheck all 3 option and close it.
Now Ask your Friend to Pm to check whether its working or not.
Credits: Dyanesh (To Remind me About It)
Thanks For Reading ^_^