Yes, kissing one’s spouse during the day of Ramadan is permissible, as long as it does not lead to intercourse or ejaculation, which would invalidate the fast.
The Prophet Muhammad ﷺ used to kiss his wives while fasting, as narrated in authentic hadith, because he had strong self-control.
However, if a person fears losing control or being led to prohibited acts during fasting hours, then it becomes haram (forbidden).
It is safest to avoid such intimacy during the day and express affection after Maghrib (sunset).