Haew Sai Waterfall contrasted the experience of most of the other waterfalls we encountered in Thailand. That was because this one was a little bit off the beaten track and hence it provided a far quieter and less crowded experience.
From what we could estimate, the falls maybe on the order of 5m or so tall (possibly 25ft tops). However, we saw it at off peak flow so the wide segmented state that we saw it in could very well be joined together into a singular continuous entity. However, if that were the case, the river would also be flooded and access to an acceptable viewing spot might be a dangerous proposition.
As for the quiet and serene experience, during the hour or so that we hiked to and relaxed at the waterfall, we were the only ones on the trail the entire time. Perhaps part of that was because we did the hike in the morning (while most people were still sleeping in their tents, I reckon), but it was still saying something considering how it seemed that everywhere we went there tended to be a crowd.
In order to access this small but attractive waterfall (maybe 10m tall), we had to deviate from the Haew Suwat Waterfall path leading to its base. Then, we took a 1km detour (in each direction) on a much narrower, overgrown, and rough track.
The track wasn't too difficult, but there were a handful of downed trees that we had to limbo under as well as a steep 100m scramble down an embankment. So given all that, I could understand why the signs said we were supposed to go with a guide (which we had one in Pang).
This waterfall starts from the same car park and uses part of the same trail as that of the Haew Suwat Waterfall. We proceeded on the path to the base of the Haew Suwat Waterfall until we were confronted with a signposted fork. And it was from that point that we took our detour.
For logistics and a few more details about accessing the car park for this falls, see the Haew Suwat Waterfall page.
To give you a sense of context, Pak Chong (where we spent the night) was about 3 hours northeast of Bangkok or 2 hours east of Ayutthaya.
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