Southeast Asia is a region bursting with people. Its cities are packed, its coasts humming with life. And yet, curiously, right in the center of this vibrant region lies a puzzling emptiness.
Pull up a population density map of mainland Southeast Asia, and something strange jumps out at you. There’s a massive, conspicuous gap. A void. A vast underpopulated zone that cuts through the heart of the region like a ghost corridor — and it aligns almost perfectly with the borders of Laos and Cambodia.
This isn’t some minor statistical quirk. It’s one of the most dramatic population density contrasts between neighboring countries anywhere in the world.
Let’s zoom in.
The Numbers Don’t Lie
Cambodia and Laos are flanked by giants. To their east, Vietnam — home to 101.6 million people, one of the most populous countries in the world. To the west, Thailand, with 71.6 million people.
Now compare that to their quieter neighbors:
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Laos: 7.9 million
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Cambodia: 17.6 million
Cambodia has about a sixth the population of Vietnam. Laos has less than a twelfth.
When you adjust for land area, the gap becomes even more jarring. Vietnam’s average population density? 322 people per square kilometer, rivaling countries like Japan or Pakistan. Thailand? 140 people per square kilometer, roughly the regional average.
Cambodia? 100 people/km².
Laos? Just 34 people/km².
That’s a tenfold difference compared to Vietnam — an almost unheard-of disparity for two countries that directly share a border.
To put it plainly: Laos is the most sparsely populated country in Southeast Asia, and the 8th least densely populated country in all of Asia, ranking closer to Mongolia, Kazakhstan, or remote Himalayan states than to any of its tropical neighbors.
But this raises a serious question.
Why?
Why is the center of Southeast Asia so anomalously empty?
Geography: The Mountains Eat People
Start with Laos. The answer begins — but doesn’t end — with geography.
Laos has an average elevation of 710 meters above sea level. That’s extremely high for Southeast Asia, a region otherwise dominated by lowland river deltas and tropical plains. The terrain is mountainous, rugged, and cloaked in dense jungle.
Nearly all of Laos is mountainous — and it shows. Only 6.2% of its territory is considered arable, the lowest percentage in mainland Southeast Asia.
Compare that with:
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Vietnam: 20.2%
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Cambodia: 22.2%
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Thailand: 30.8%
Laos isn’t just less arable — it’s geographically smaller than the others too, meaning the total amount of land available for farming is minuscule:
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Laos has ⅓ the arable land of Cambodia
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⅕ that of Vietnam
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⅒ that of Thailand
In short, it’s very hard to farm in Laos. And that’s a big deal in a region where agriculture still underpins much of rural life.
Yet geography doesn’t explain everything.
Laos, after all, has more arable land than South Korea, a country with over 50 million people. And while it’s mountainous, so is Yunnan Province in China, just across the border — which is more than four times as densely populated.
So what gives?
Cambodia: The Flat Enigma
If Laos is mountainous and hard to farm, Cambodia isn’t. Cambodia is flat. Very flat. And it’s not landlocked — it has direct access to the sea.
Its arable land percentage is comparable to Vietnam’s. Its terrain is conducive to development. It even has the Mekong River, a vital trade artery that flows directly to the sea.
And yet, Cambodia is still relatively empty.
To solve the mystery, we need to go deeper — because it turns out this puzzle isn’t just about geography.
It’s also about history.
The Secret Weapon: Vietnam’s Super-Rivers
Vietnam’s population isn’t evenly spread out. Most people live in just two places: the Red River Delta in the north and the Mekong Delta in the south.
These aren’t just ordinary fertile lands. They are two of the five most agriculturally productive river deltas in the world.
The Mekong Delta alone — a sprawling, Netherlands-sized expanse of rice fields, canals, and nutrient-rich mud — produces 60% of Vietnam’s rice. The Red River Delta, birthplace of Vietnamese civilization, produces another 20%, despite occupying only 5% of the land.
That’s 80% of Vietnam’s rice coming from two river deltas.
The Mekong alone deposits 1 billion cubic meters of sediment into the delta each year, advancing the land 60–80 meters into the sea annually. These natural deposits continuously fertilize the soil, making three rice crops a year possible — a rare agricultural feat.
The deltas are the engines of Vietnam’s agricultural dominance. And they’re where 60% of the population lives.
That’s the kind of geography that builds civilizations.
Cambodia, by contrast, has fertile areas — but none quite like Vietnam’s deltas. And it lacks the same level of integration into global trade networks. While Vietnam has a long coastline and is tightly linked to China’s massive economy, Cambodia is tucked between neighbors, with a small coastline and no massive delta engine.
And as for Laos — it has no coastline at all.
The Landlocked Prison of Laos
Laos is the only landlocked country in Southeast Asia, boxed in by Thailand, Cambodia, Vietnam, China, and Myanmar.
But being landlocked is just the start of its problems. Most of Laos’s borders are with mountains. That means even trade with its neighbors is hard.
Here’s a mind-bending fact: the border between Laos and Vietnam is so remote that it harbored an undiscovered species of megafauna until the 1990s — the Saola, a 100-kilogram wild ox, unknown to science until 1992. The terrain is that inaccessible.
Even the Mekong River, which runs through Laos, is unusable for trade. Why? Because of the Khone Falls — the widest waterfall in the world (11 kilometers across), located at the Laos–Cambodia border. It completely blocks river traffic.
Cambodia and Vietnam, downstream from the falls, can trade via the river. Laos? Stuck.
It’s landlocked, mountain-locked, and waterfall-locked — a triple whammy of geographic isolation.
The Bomb Cratered Countryside
And then… there’s the war.
From the 1960s to the 1970s, Laos and Cambodia were plunged into one of the most destructive periods in modern history — all tied to the Cold War, the Vietnam War, and massive covert operations by the United States.
Start with Laos.
To disrupt the North Vietnamese supply chain — the infamous Ho Chi Minh Trail, which ran through Laos — the US launched what is now the largest aerial bombing campaign in history.
From 1964 to 1973:
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580,000 bombing missions were flown over Laos
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Bombs were dropped every 8 minutes, 24 hours a day, for 9 straight years
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Over 2 million tons of bombs were dropped — more than the US dropped on all of Europe and Japan in WWII
Most of them were cluster munitions — which released dozens of mini-bombs on impact. An estimated 80 million of these remain unexploded across the countryside.
To this day, 30% of Laos’s territory is contaminated by unexploded ordnance. Entire swaths of farmland are off-limits. Since the war ended, more than 20,000 people have been killed by leftover bombs. And full cleanup could take another 100 years.
Laos didn’t just get bombed. It got cratered.
Cambodia’s Genocide
But if you think that’s grim, the situation in Cambodia was even worse.
In the 1970s, Cambodia endured carpet bombing, a civil war, and then one of the most extreme and horrifying regimes in history: the Khmer Rouge.
Led by Pol Pot, the Khmer Rouge took over in 1975 and immediately emptied the cities, declaring it “Year Zero”. Money, religion, families, and education were abolished. Everyone was forced into slave labor on collective farms.
What followed was a genocide:
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2 million people were killed, or 26% of Cambodia’s population
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20,000 mass graves — the infamous killing fields — have been discovered
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Doctors, teachers, monks, and anyone with glasses were executed
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Ethnic minorities were massacred or forced out
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Nearly 7 million Cambodians who should exist today… don’t
By the time Vietnam invaded in 1978 and ended the Khmer Rouge regime, the demographic landscape of Cambodia had been gutted.
It still hasn’t fully recovered.
Today: The Legacy of Emptiness
Look at a satellite map of Southeast Asia at night. You’ll see brilliant clusters of light across Vietnam and Thailand.
Then — darkness — across Cambodia and Laos.
But the story isn’t static.
Since the 1990s, Cambodia and Laos have been making a comeback.
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Cambodia’s population has more than doubled since 1989
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Laos is also growing steadily
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Both still have fertility rates above replacement level
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Meanwhile, Thailand and Vietnam are shrinking
Thailand’s fertility rate is now 1 child per woman, one of the lowest on Earth. Vietnam’s just dipped below replacement in 2023, and it’s projected to begin shrinking in the 2050s.
Which means that sometime in the future, the “void” in the center of Southeast Asia might not seem quite so empty anymore.
But the shadows of the past — the mountains, the bombs, the genocide — still linger in the map.
FAQ
Q: Why is Laos so sparsely populated?
A: Geographic isolation (mountains, no coast, low arable land), heavy wartime destruction, and unexploded bombs still affecting development today.
Q: Why isn’t Cambodia more populous if it has arable land?
A: Because of the Khmer Rouge genocide in the 1970s, which killed 26% of the population and stunted demographic growth for decades.
Q: Why is Vietnam so densely populated?
A: It controls two of the world’s most fertile and productive river deltas — the Mekong and the Red River deltas — enabling massive, sustainable agricultural development.
Q: Could Laos or Cambodia catch up in population?
A: Possibly. Both countries have positive fertility rates, unlike Vietnam or Thailand. But infrastructure, education, and economic development are critical limiting factors.
Q: How long will it take to clean up the bombs in Laos?
A: Estimates suggest it could take over 100 years to remove all unexploded ordnance from Laos’s countryside.
Q: Are there still unexplored areas in Laos?
A: Yes — some regions, especially along the Laos–Vietnam border, remain so remote that large species (like the saola) were only discovered in the 1990s.
