In Pokémon Movie 2000, Melody gave Ash a “traditional greeting kiss,” causing Misty to get all jealous.
What makes this one interesting, is that we are unsure who gave Ash the kiss. It could’ve been Latias as Bianca or actually Bianca (read evidence for each theory here).
As Kotaku previously pointed out, in Pokémon XYZ, Serena’s crush on Ash is canon.
At the end of 2002’s Pokémon Heroes, a girl gives Ash a peck on the cheek.