Beyond Thong Pha Phum the views get increasingly spectacular as Highway 323 climbs through the remaining swathes of montane rainforest, occasionally hugging the eastern shore of the Vajiralongkorn Reservoir until 73km later it comes to an end at Sangkhlaburi (often called Sangkhla for short). In the early 1980s, the old town was lost under the rising waters of the newly created Khao Laem (now Vajiralongkorn) Reservoir. Its residents were relocated to the northeastern tip of the lake, beside the Songkalia River, where modern-day Sangkhla now enjoys an eerily beautiful view of semi-submerged trees and raft houses. It’s a tiny town with no unmissable attractions, but the atmosphere is pleasantly low-key and the best of the accommodation occupies scenic lakeside spots so it’s a great place to slow down for a while.
Cultural interest is to be found in the villages, markets and temples of the area’s Mon, Karen and Thai populations, including at Ban Waeng Ka across the water, and there’s natural beauty in various waterfalls, whitewater rivers and the remote Thung Yai Naresuan Wildlife Sanctuary. It sees relatively few farang tourists, but it’s a popular destination for weekending Thais (come during the week for better deals on accommodation) and resident NGO volunteers add a positive vibe. Though the Burmese border is just 22km away at Three Pagodas Pass, at the time of writing it was closed to foreigners.