Geography is not my strong suit but the real reason I haven't heard of any of these cities beside Manila is because they are parts of a larger urban environment. Indeed, many are either in Metro Manila or Bengal. The distribution is either in India or the Philippines, with the number ten entry being the joker in the packed; being in France.
But, if the Hooghly River features in the background in many of these congested regions, clearly the city category differs from that of a discrete metropolis.
Yokohama has 8,500 people per square kilometre it says at one source; elsewhere a scribe opines how it is difficult to measure the population of Tokyo and produces instead a table that shows the prefectures and their respective densities. I can hazard a guess and say that density when compared to the "cities proper" on the list, is not that bad.
Manila is most crowded and has the sixth highest urban population so we know it's in for a Best of Congest award.
One figure that may rock your world - Titagarh has a tiny population teetering between 114 thousand and 124 thousand. Yes, it's in West Bengal with the second highest density of a city proper.
And France isn't a one-off in the tightly packed stakes as the runner-up with 67,047 people per square kilometre is Le Pre-Saint-Gervais.