Before coming to Vietnam I'd visited most of the other Southeast Asian countries and in any of the major cities there were districts that were considered slums. For example, in Manila there is the infamous Tondo.
The surprising thing is that in Ho Chi Minh City there's nowhere that I would especially consider a slum region. The city has some richer and poorer neighborhoods but most of the city is fairly uniformly poor and underdeveloped yet safe and economically thriving. There is no Cabrini Green (Chicago) projects or massively dense and lawless Kowloon (Hong Kong).
Some regional stats:
Access to water in urbanized areas of...
1. Indonesia: 89%
2. Philippines: 93%
3. Vietnam: 99%
Access to sanitation in urbanized areas of...
1. Indonesia: 67%
2. Philippines: 80%
3. Vietnam: 94%