Strictly focusing on what I've seen so far.
P'Korn and Champage will be the other love line, Yui and Pu will be the other, and Doctor and Than's Sister.
Yui and Pu's love line was shared before the lakorn starting sharing. Although she has a deep love for P'Korn, her silly self will eventually fall for Pu and vice versa because it seems like he only sees her as the boy crazy ditzy best friend of Kew but perhaps through hardships and disappointment they'll fall for each other. Hahaha
P'Korn and Champage(?) although obvious, since they're the only other major coupling shown in the intro, it could always just be an act but I doubt it. Thinking about it they'd be cute together thinking about their characters. P'Korn so far we've seen how he is with his tomboyish yet a bit childish sister Kew, her best friend boy crazy Yui, and Than's sister...who all are a bit "childish" and are all younger sisters to someone. It'd be more interesting for him to be with a possible n'rai or spitefire like Champage who will be a bit of n'rai because of her jealously and interest towards P'Korn, And who knows, maybe to prevent her being troublesome to Than and Kew, he'll interfere...and I see bickering yet fondness that can develop between the two. Just look at the intro and how they endearing reached for one another's hair/head when getting off the motorcycle.
Doctor and Than's sister, I kind of feel is obvious. She seems to follow him like a little puppy, and she does seem interested in him. But it seems like he's either too dense too notice or wants to keep it professional since her brother is his patient. Age/look wise they seem more like an appropriate match too. Maybe in the beginning her and P'Korn are just used to be an extra side bickering and interesting angle for audience to see play on, but I think these two will be a couple in the end.
I think Mario and Mint are both doing great so far with acting. I feel both have received mixed reviews with each new character they play, but I think this lakorn and their characters so far is a good representation of the amazing progress they've made. Mario like Mint has done a few dramas so far and worked with and will work with a varied group of actresses like how Mint works with a variety of leading men but neither has found the "it" project for them yet. I think this one could be a good shot for the both of them.
Offscreen they seem to compliment each other well too. Mario seems like a undercover mischievous one while Mint is openly mischievous yet they both have a reserved and certain "class" and laid back vibe to them. I'm really interested in what the Thai audience thinks about the pairing so far.