A Ho-Oh appeared to Ash at the end of the first episode, flying
alongside a rainbow across the sky after the thunderstorm.
competing in the Silver Conference, Ash saw Ho-Oh flying towards
Hoenn. This encouraged him to get over his depression at his loss and
continue his journey.
Ho-Oh was seen flying into the sunset at the end
of Battling the Enemy Within!. This time, Brock, May, Max, Scott and
Brandon saw Ho-Oh as well (on a slightly related note, this time,
someone other than Ash managed to identify it first).
So yes, Ash sees Ho-Oh many more times after the first episode