There is a video that explains it a little more here: http://www.talktomeinkorean.com/shows/askhyojin15/ The website is also very helpful for learning Korean in general. Hope this helps :)

방콕 is that 방(에서) 콕 (박혀있다). Meaning of that is" I didnt do anything at home." It is slang.

As the person above said, it means like I stayed at home with doing nothing :) I think that expression would be relevant when you speak with your friend.