I take back what I said earlier about Matt being a "safe" choice, because that perpetuates that unhealthy fan culture thinking where being in a relationship is deemed fine if cast opposite a single/"koo-jin" co-star. It shouldn't matter whether someone is or isn't in a relationship because at the end of the day all these actresses and actors are just doing their jobs, it's up to the fans themselves to take a step back and separate REEL from REAL.
As for Nadech it might not seem like it but I genuinely am rooting for him, I see so much potential for him outside of the whole "koo-jin" tag.