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first off, id recommend to read the manhwa, but here is kind of a short dive into jay's character with possibly light spoilers ahead, depending on the person.

from my interpretation, jay initially assumes yoohan (or sun in the thai adaptation) is just another normal looking aspiring actor trying to get close to him for personal gain, as he is the director and is used to people approaching him due to his status, money, influence, etc.

however, a deeper reason is that jay is an extremely possessive and emotionally warped character. he is fascinated by yoohan, but isn't really capable of handling being vulnerable in a "healthy way," instead trying to establish control over the situation rather than openly expressing his true feelings. his punch is more of show of jay's need for control, arrogance, and inability to deal with people who affect him emotionally.

additionally, about the money, a more or less spoiler free version of events is that 5 years prior yoohan and jay had crossed paths and ended up having sex, and yoohan payed him 200 won (lee baek won), doing the same with the cigarette. at that time, yoohan wore a bunny costume, so jay count see his face, and 5 years later we are shown that he is still trying to find yoohan "the bunny." this may have caused jay to feel somewhat vulnerable, and like "woah what the hell" as yoohan pulled the same thing as his bunny. and honestly jay sucks at vulnerability, resulting to intimidation, provocation, or aggression, which make a lot of his interactions with yoohan feel hostile and charged.

i wouldn't say "oh jay punched yoohan because he liked him" or sm, but rather "jay punched him because he misjudged him, wanted to assert control, and was already emotionally affected by him."

jay isn't written as a "normal" male lead, cause a lot of his early behaviour is genuinely unhinged and the story doesn't really pretend otherwise.