Yeah it’s palatines voice inside kylo head, the dialogue goes something like this :
Palps -“the jedi apprentice lives, I hope you’re not trying to decieve me, dont make me turn my fleet against yours”
Kylo -“I know where she is going”
Palps -“good, kill her!”
So it isn’t a hologram, but it serves the same purpose. The dialogue definitely makes it look like Kylo is just following his orders. Sure, he has other plans, but functionally he is just doing what he wants. Kylo should be doing the opposite, if we want him to have any agency in this film.