The Rainbow Waterfall

Nam Tok Sai Rung — the Rainbow Waterfall — sits inside Ramkhamhaeng National Park in Sukhothai’s Khiri Mat district, tumbling down four tiers through a gorge more than 100 metres deep. It’s not free: entering the park costs 200 THB for foreign adults (100 THB for children) and 40 THB for Thai adults (20 THB for children), same as anywhere else inside the park boundary. The rainbow effect that gives the falls its name shows up when sunlight catches the spray at the right angle — reliably between about 11:00 and 16:00, not at dawn as some travel guides claim.

From the ranger checkpoint, a streamside trail follows the water upstream for 800 metres to 1.2 km, depending on which of the four tiers you’re aiming for. The lower sections are the easiest reach and the most popular for wading in the shallow pools that collect between drops. Higher up, the trail gets steeper and rockier, and the spray keeps the path slick even in dry weather. Moss-covered boulders and overhanging trees frame each tier, and the roar of falling water carries a fair distance through the forest before the trail even reaches the first cascade.

Water volume swings hard with the seasons. June through October — the rainy season — brings the fullest, most photogenic flow, though heavier cloud cover on any given day can mean no rainbow at all. Drier months thin the water to a fraction of its wet-season self, sometimes barely a cascade, though clearer skies improve the odds of catching the light show when there’s enough spray to catch it. There’s a real trade-off here: chase volume, or chase sunshine, because you rarely get both at once.

Insider Tip: Aim for a visit around midday on a day with scattered rather than solid cloud — direct sun plus fine mist is the combination that actually produces the rainbow, and locals time trips for exactly this window rather than the cooler early morning most Thailand guides recommend for hiking.

Watch out: the trail crosses the stream more than once, and after rain the crossings can be ankle-to-knee deep with a real current. Wear shoes with grip, not flip-flops, and don’t push further upstream than the marked trail if the water’s running high — the gorge walls are steep enough that a slip matters.

Combine the visit with Ramkhamhaeng National Park (Khao Luang) for the summit trails, or head to Si Satchanalai National Park for a second, less-visited waterfall circuit nearby.