If K is a bounded operator on a separable Hilbert space \( \mathcal {H} \) , we will characterize scalable K-frames with respect to positive diagonal operators on the sequence space \( \ell ^2 \) . This is the simplest method to generate a Parseval K-frame without requiring the invertibility of frame operator. One first goal is to modify the content of Theorem 3.8 of Ramesan (Mat Vesn 75:225–234, 2023) (and Theorem 4.1 of Ramesan (Palest J Math 12:493–500, 2023)). First, we provide a counterexample to its invalidity and then we prove it with an additional assumption. We also investigate the stability of scalable K-frames under suitable operators.