Is it okay to cite a TED presentation or a video lecture or something similar? If so, how to cite that video for your paper/thesis?
A quick google "apa cite video" would give you lots of advice, such as http://www.easybib.com/guides/citation-guides/apa-format/youtube-video/ which notes:
Last Name, F.M. [Username]. (Year, Month Date). Title of video. [Video File]. Retrieved from URL.
I would recommend citing the talk or video in a footnote, and then you can probably refer to it as 'So-and-so video' throughout your paper. That way readers will know that they can watch the video if they want more information.
I would also recommend linking the talk or video to your bibliography. You can do this by saying 'see So-and-so video' in parenthesis next to the place where you cite it, but that's just my personal preference.
As for citing it in the body of your paper, you can say something like 'So-and-so (video) argues that X.' So you will want to cite the video or talk and then mention in parenthesis that they made this argument. This can be done by saying something like 'According to So-and-so (video), p.' You should then provide a page number where this is discussed.
I don't recommend you do this, but if you really wanted to, you could say something like: 'So-and-so argues that X.' and then quote the speaker directly.
That's about it. If you are going to use a lot of TED videos in your paper, I would recommend making a list of them and citing each one accordingly.