Two days of heavy rain have caused flash flooding in the park and filled the Lam Takhong River to capacity.
Trees near the Hom and Pak Chong entrances have been uprooted from the rain-softened soil, while landslides are also blocking access at several points, said park chief Narin Pinsakul on Friday morning.
The clear-up operation would take 2-3 days before the park is safe for visitors, he added.