There was a foreign speaker participating over Skype. As idiotic as the law seems to be, I do believe the case is rather clear. The foreigner did indeed speak at the conference, which was public. The fact that Skype was used as a medium to facilitate that doesn't really change anything.
If I rant against Disney land with the dealt penalty, and the video is later played there, I have not given a speech there.
If someone live-streams a keynote and a Q/A session as a part of an event, then the person speaking is obviously participating.
Please note, that I have no problems with remote participation of events. It just happens that our favourite south-east asian police state requires a permit for such events. Our opinions on whether that law is a good one or not has nothing to do with the medium chosen for the event.
The right to free assembly isn't a thing in Singapore apparently.
Rich does not equate to equitable. Dubai and Qatar are other examples.