So I read this on one of Taew's fanpages
This scene is the part where Nok finds out that when she was drunk, Nai brought her to his room and not hers. She gets so mad that she comes to his room dumping trash on his head and slapping him. She doesn't let him explain what happened. Nai doesn't want to argue much so he says "Next Time if you slap, I'll kiss."
[Behind the scene]
This scene was filmed in a hotel at Huahin, Taew and JJ had to have strong emotions for the scene and the lines were long. Taew came into JJ's room, dumped trash on him, slapped and insulted him. However when they were rehearsing the scene, Taew didn't slap JJ that hard. But when they were actually filming, JJ told Taew to give her all. So Taew gave her all and she was so into the character that she slapped JJ so hard to the point where it made a very loud noise and the whole crew was shocked. JJ turned red from face to neck. The lines were really long so they had to film this part around 5 times. JJ got slapped continuously and when they finished the scene, Taew asked him if he was hurt. JJ was in so much pain he could barely talk but he later admitted that it hurt a lot. Taew said sorry right away. This scene took a long time to film and they had to bring their emotion to the highest point. Therefore, that part that JJ said "Next time if you slap, I'll kiss" actually felt real and not that he was acting anymore.
When I saw this scene in the mv, I could feel the pain