I think there must be typos in your K and S - the parentheses do not match. I get (with no warranty express or implied):

let K = A(A(A))(A(A(A))(A)(A)(A)(A)(A));

let S = A(A(A(A)(A(A)(A(A)))(A(A(A(A)(A(A)))))))(A)(A);

> Eager languages can be made lazy by wrapping arguments in lambdas with dummy arguments

So, something like this?

let A = x => y => z => () => x()(z())(y()(w=>z()));