This place is in Kanchanaburi Province. Go to Erawan Waterfall and just passed that there is a turn off to your left to Srinakharin Dam National Park. Only 42 kms thereafter on a very rough no tarmac road you will reach it. This was my second time there, but went there on that rough road. Near on 2 hours on that road to go 42 kms. I would not advise this road. Use the other route.
The first time, I went the long way around on an easier way, on two ferries across the Srinakarin Reservoir. Great views there as well along that way. Go during the “Rainy Season” then the Waterfall should be as full as you have see in my photo.
Should you wish to go there, take a Thai with you that knows the area and way.
Took me 4 hours there, 1 click as you saw, 4 hours back with a whole group of people. On your own it should not take you that long.