Mae Nam Song Si

Mae Nam Song Si means two-colour river, and it describes the confluence at Khong Chiam where the Mun, Thailand's second longest river, enters the Mekong. The two carry different sediment loads and the Mun tends to run clearer and bluer against the Mekong's heavier brown, so for a stretch below the junction the waters run visibly side by side before mixing. The contrast is strongest in the cool and dry months when flows are lower and the Mun is clearest; in the wet season both run brown and the effect largely disappears, which catches out visitors who arrive in August expecting the postcard. There is a viewpoint park on the Thai bank and long-tail boats run out from the pier to sit on the line, which is the better way to see it. Laos is on the far bank. Khong Chiam is a small town at the easternmost point of Thailand.

What you actually see

• The two colours - the clearer Mun against the brown Mekong below the junction.
• The viewpoint park - the Thai bank overlook at the confluence.
• The boat trips - long-tails running out onto the line itself.
• Laos across the water - the far bank of the Mekong.

When to go

November to February, when low flows make the colour contrast clearest. In the wet season both rivers run brown and the effect is largely absent.

Honest expectations

The two-colour effect is seasonal and much weaker or absent in the rains. It is a subtle line rather than a sharp division. Khong Chiam is small with limited services and a long drive from Ubon.

Nearby

Pha Taem National Park and its rock paintings are north; Kaeng Tana is west along the Mun.