the answer you are looking for is kash but...
kaysh, kashay, and katch are all blatantly wrong. THIS IS FRENCH. kash is closest to the correct pronunciation, but the real pronunciation is kahsh, with the 'ah' as in 'hot'.
i mean the anglicized version would be kash, but its not the original. the rest of them are just blatantly wrong. french does not have a tch sound, kashay is wrong cuz theres no accent, and kaysh is just... NO. if it was pronounced kaysh, then the spelling would be kéche, so ja.....
for french words, youve GOTTA understand french pronunciation, cuz it is NOT english pronunciation. oh my goodness how they are different!!!!!
EDIT: for the record, if you pronounce it kashay, that either implies the word is cacher or that it is caché. cache is a hiding place, but caché is an ADJECTIVE meaning HIDDEN. cacher means to hide. so pronounce is kahsh, or you get into a MESS of weird lingual stuff.
Another Edit: did someone just vote this as not useful? im here to give the actual correct pronunciation, along with the anglicized pronunciation, so if you have some sort of problem with the correct pronunciation, then...