Cletus - he’s correct for mandarin, not sure on cantonese/korean, but in Japanese it is pronounced ‘coon’ as in raccoon.
My wife is Japanese and between the shows she and my daughters watch I hear it all the time. Alas - my Wife never used it with me even when we were dating :(
So Cletus-kuhn would sound like Cletus-coon.
Is the “u” in Kun as long drawn-out as in racoon?