We are given the system of linear equations:
\[
2x + 3y = 6 \quad {(Equation 1)}
\]
\[
4x + 6y = 3k \quad {(Equation 2)}.
\]
To determine the value of \( k \) for which the system has at least one solution, we first observe that Equation 2 is just Equation 1 multiplied by 2:
\[
4x + 6y = 2(2x + 3y) = 2 \times 6 = 12.
\]
Thus, Equation 2 becomes:
\[
4x + 6y = 12.
\]
Now, for the system to have at least one solution, the right-hand sides of both equations must be consistent. Therefore, for Equation 2 to be consistent with Equation 1, we must have:
\[
3k = 12 \quad \Rightarrow \quad k = \frac{12}{3} = 4.
\]
Thus, the value of \( k \) is \( \boxed{4} \).