Whether you're team Khem or team Su, what I find interesting now is their reaction once they got back to Thailand.
Khem who supposedly set up the perfect trap in Switzerland, seems to be completely erratic, adds now insults to humiliation, harasses & stalks Su when he was the one who asked her in his letter to get out of his life. Su, on the other hand, now that she's dried her tears, seems focused, ready to move on and for a fight whenever Khem shows up, which is all the time !
However wounded Khem feels, I do think that he crossed the line with his masterplan (Day 4 = sleep with the ex, check - Day 5 = dump the ex, check - propose to new girlfriend, check ) + the bonus : blackmailing Su to help Gane with the wedding... But at the end, Su is able to deal with it and he's the one losing it, with Gane as collateral damage.