All the definiting and criteria are confusing. Saying there is or isn't a slum is mostly semantic. You might say all of Vietnam was a slum by most Western standards. Whether there are slums or not in Ho Chi Minh City, anywhere you look in Vietnam you're going to find poor people living with poor infrastructure where the government can basically take land at will.
But if you came here for slum tourism then maybe you should take a bus to Phnom Penh instead and visit the Steung Meanchey garbage dump, a.k.a. Smoky Mount