There are many great hiking trails in Malaysia, but some of the most popular include:
Gunung Mulu National Park: This UNESCO World Heritage site is known for its limestone karst formations and offers several challenging hiking trails, including the Pinnacles Trail and the Headhunters' Trail.
Mount Kinabalu: This mountain in Sabah is the highest in Southeast Asia and offers several hiking trails, including the Via Ferrata, which is a challenging climb that requires the use of fixed cables and ladders.
Bako National Park: This park in Sarawak is known for its rugged coastal cliffs and offers several hiking trails, including the Lintang Trail which offers great views of the coast and the jungle.
Taman Negara: This national park in Pahang offers several hiking trails, including the Canopy Walkway, which is a suspended bridge that offers great views of the rainforest canopy.
Mount Tahan: This mountain in Pahang is the highest in Peninsular Malaysia and offers a challenging hike that takes several days to complete.
Note that these trails can be challenging and some of them will require permits and guides, it's advisable to check the current situation and regulations due to the COVID-19 pandemics.