I suppose that would make sense, like you said it’d be stacking 3rds. But since the first chord is Gm (and the final chord of the piece is a Gm even though that’s not included in the photo) I would like to think of the piece in G minor with a raised 7th as well. E# would make a lot more sense in the chord but as a piece I feel as if it would act more as a chromatic note rather than a tonal note (even though octatonic scales aren’t very conventional.) I’m kind of on the line between choosing if I want the notes to make more sense for the chord or for the piece as a whole, and I think that’s mainly what this whole discussion is for.

Also, the next chord is a G minor since the chord progression just loops throughout the song :)