Updated 14-Sep-2023
Ob Khan National Park is about 40 minutes from Hang Dong market. Starting at the road which goes West from the Rectangle Coffee X Tower, it is more or less a straight (meandering) drive of 22 minutes (according to Google).
In the Alltrails site, there are several different hikes with Ob Khan in the name, at least two are quite misleading on the map, and only plotted and reviewed by one person. There are two basic trails to walk.
Main trail upriver
The main trail starts out at the Ranger's station (next to the coffee shop) and is a fairly well-marked trail that meanders along the river, going upstream on the right-hand side. Some of the trail is along the sandy riverbank, and others are steps cut into the walls. There is an iron bridge (posted maximum 8 persons at a time), that then crosses over and loops back and up and over a steep hill. There are some rails and ropes offering minimal protection from a steep slide. This is very challenging for small children, and on the iron bridge, there are no safety guides to prevent a child from falling many meters into the rocks below.
Overall the walk is a bit rocky, so sturdy walking shoes are a must. It is possible to bring swimming clothes / towels / change of clothes and just walk up the trail until a good spot in the river is found, and go swimming. Just past the iron bridge it is a bit shaded, which makes it nice, though the rocks can be sharp. Water shoes or water sandals can make it more comfortable. The water current can be strong through the restricted gorge.
There is a sign saying to not go beyond that point just past the iron bridge, and so walking across and looping over a hill back to the park facilities is the only choice available, other than going back the way one came.
Bring water, snacks, sun protection (hads, jackets, long pants) and sturdy shoes.
Second trail downriver
The downriver trail simply follows the river bounded by forest and farms, and doesn't include gorge scenery.
There is an intermediary link between the two trails which is also walkable and quite stunning, as a valley spreads out bounded by very tall trees but with a sweeping view. The whole area is interesting to explore.
Amenities, Availability, Contact
This area is perfect for picnicking. They have bathroom facilities and also a small cafe. Further back before the park entrance, there are sometimes one or two vendors set up with snacks for sale (usually weekends but not necessarily weekdays). An ice cream vendor may show up on hot weekend afternoons. There is a large grassy area set aside for camping, which can be reserved, though there are signs posted that this area is not for barbecuing. Note that there while there are ample toilets there are no showers.
Ob Khan has gotten a newly paved road that was finished on 20 March 2022, and the trails are fairly well laid out, though sometimes one has to double back as the trails can be faint over the hard surfaces. The open hours were updated recently updated on Google Maps and Facebook, are set from 8:30 am until 5 pm, daily. Email: , Phone: 086 181 1068, Facebook page.
There is a camping area that can be reserved during the cool and hot seasons, but is not available during the rainy months.