Are ballads kpop songs ?

Kpop classification depends on how artist, not the genre. The usual traits of kpop are being a trainee training under a company before debuting, have choreography, having visual members. if you fit these traits your music will be classified as kpop.

EXO doing ballads is kpop but Park Hyo Shin doing ballads is not Kpop.

doesn't one have to remember that kpop isn't a genre per se but rather just korean popular music which includes so many actual genres one of them happens to be ballads