Over the decades, over all, we made good money buying and eventually selling real estate in America. On occasion, we also lost money. In most cases this was property that we actually lived in, even if it was an apartment building. We also own property in Viet Nam and have investigated buying property in TP HCM.
The most important thing is to understand your specific situation. Depending on a person's specific situation, buying any specific property can be a wise decision or a horrible mistake.
One "rule of thumb" is that renting is better than buying if you are going to live in a property for less than 5 years. For someone who is interested in buying a long term residence, I suspect that they will likely do reasonably well.
As to buying a property to rent as an investment, I'm living in a rented house, owned by a very intelligent Vietnamese family; who nearly got in serious legal trouble for, previously and unknowingly, renting this house to a Chinese criminal gang. As others have pointed out, the higher end, or foreigner market is already oversupplied and supply is rapidly being expanded by new construction. Personally, I suspect that buying rental property, at this point in time, in TP HCM is a bad idea for most foreigners.