I spent 4 years in Vietnam and 2 of those traveling 15,000km+ by motorbike (across Vietnam, Cambodia, Laos). I've been to the remotest parts you can possibly get to and seen more than even the locals have of their own countries.
All three of these countries are eco-nightmares.
They've dammed up all the rivers in the north, which has affected just about everything. When the rivers are running during the wet season, there is plenty of power, but as soon as the dry season rolls around, entire rivers run dry. Only to have massive flooding when it rains again. Slash and burn entire mountains for farming, so that when it does rain, there are massive landslides.
The trash and pollution is out of control. It is literally in the culture to use plastic, for everything and to just dump/burn it everywhere. There isn't a single place that isn't rife with trash.
Don't get me wrong, I absolutely love the country and the people are lovely. I just wish they cared about what they are doing to the planet a bit more. The government controls what the people think (case in point, the helmet "law") and abysmal education of their people. They could easily tell people to cut down their plastic/trash usage... or stop blocking all the rivers... but that's not in line with profit/corruption... so it won't ever happen.