It is a vakra-shadava-sampurna rāgam (vakra-shadava, meaning 6 notes in ascending scale with zig-zag moves).
Later with the usage in javalis and other later compositions, the bhashanga type of Khamas came into use (using notes external to the scale).
[1] Kakali nishadam (N3) is introduced as anya swara (external note) occasionally.
[1] According to Muthuswami Dikshitar school of music, Khamas is a sampurna raga with no zig-zag notes (no vakra usage).
The Hindi film song ‘Tere Mere Milan Ki’ from the movie Abhimaan is based on Khamaj.