I was questioning this too… I hope there is a reason for this and will be shown as a backstory…
I think nuea never thought about telling his feeling to kluen it was his frd that suggest him to tell.... remember his frd told nuea that even if you tell him or not the result will be same, so at least leave before telling him. He has to leave the country so at he leave telling his feeling to his crush. Kluen maybe surprised n also sad thats y he didn't say a word just told him have a save flight. N the last part I think u maybe right but kluen is open about his feeling just nuea is not noticing him. He is too busy thinking that kluen have gia. Ps : English is my fourth language if there is mistake kindly ignore them.
Ps : English is my fourth language if there is mistake kindly ignore them.