Can a conference paper be an extended version of a previous conference paper? Will it face copyright issues?
It would seem that you should contact the organizing committee of the conference and get their advice. To me it seems kind of low to write papers that have very similar content but it does happen.  If you are questioning it that much I would bring it up with the Organizing Committee and see what they say. You don't even have to mention names or specifics but just get their general opinion.