I need to translate this phrase below. The only context I've been given is that it's something a girl said to a boy.

"ร้องให้ ซึ้งมากรึไง"

I can translate it word for word, but I'm really not sure of the meaning of ซึ้ง

It almost sounds like "I cried. Are you that stupid or what?"

or maybe "I cried. Is it that hard to see?"

But . . . I'm actually not even sure if the speaker is crying, or implying something entirely different . . .

no, ซื้ง means like kind of "full of emotions" or emotional

Often used when you are emotionally sad or touched by something.

So the translation of "ร้องให้ ซึ้งมากรึไง" would be "You're crying. Was it that emotional/touching?"