Who wrote a novel called Tattoo perhaps published in 1970s about young experiences growing up and at war SE Asia Korea?

The novel you're describing is likely "Tattoo" by Greg Matthews, published in 1975. It explores the themes of youth, identity, and war through the experiences of a young man named Toby growing up in Australia and later serving in the Vietnam War.

While the novel focuses on Vietnam, it also touches on the Korean War, as Toby's father served in that conflict.

Are you looking for more information about the novel or Greg Matthews? I'd be happy to help!