Obviously it's Nadech.
IMO, Nadech and Boy have bigger fanbase compare with the rest of the boys. And of course Mark also has very hardcore followers. It's overwhalming for me everytime to see crowds going crazy over Nadech in every event he goes.
But besides his broad mass awareness and popularity, what set Nadech apart from other peeps in the same generation is that he is the one getting most recognition for his talents from media and practitioners within ET. Just look at how many awards he's got nominated and won for two short years. It's amazing he won important awards like maekala and tvpool at such a young age. Now a days it's a time dara can get a lot of fans just being a IG whore on social networks. You could flirt with as many girls as you want on IG and twitter and doing love promo all the time to get attention and stay popular. But whether you're talent enough to get recognized, it's another story.