The short form ku is less common than the long form. In some cases, these two forms appear to be in free variation, but the short form typically occurs in wh-contructions or relativization (Hagemeijer 2000).
Ke se me ku n sêbê ku a mata tudu mana mu nê.
[house DEM proper REL 1SG know COMP IMPERS kill all sister POSS in.3SG]
'The house where I know they killed all my sisters.'
IMPRS = impersonal pronoun