I'll let other people go to crowded cities, while I will be heading to Alaska in a week.
But here's something that bothers me. Saigon and other Oriental cities show horrible street traffic and crowded housing. Yet, when you look at the statistics, they don't show up in the list of highest population densities.
Here's an example:
https://en.wikipedia.org/wiki/List_of_cities_by_population_density. In this list of 42 cities, Paris shows up along with 6 other French cities. The Philippines have 9 cities on the list, but Vietnam, Thailand, and Hong Kong are absent.
My theory is that some cities have extremely crowding problems in the center, while the outer areas are not bad. That drives down the people-per-mile statistics, and it does not look too bad. But the reality is that tourists all flock to the center, because there's nothing much of interest in the outskirts.
Hence, all the travel and youtube videos I see of Oriental cities show people on top of one another, while I have been to Paris quite a few times and it is not as bad as the order on the above list suggests.
Another explanation is that Paris residences are mostly apartments in multi-level buildings. Hence, there are a lot of people per square mile, but if they don't all flock to the street in scooters, you don't have the congestion and pollution as in Oriental cities.