Mid middle class since you don't own the landed property 100%.

To be in the upper middle class, you need to own a private property 100% and live in it.

IMO, those who own and live in a HDB flat and buy a private property (second property) to rent out is still considered mid middle class. If they don't have tenant to pay for the mortgage, they will likely not able to finance the mortgage comfortably. In a crisis, there will be no tenants and rents will plunge. This group will panic and will need to sell their investment property urgently. Fire sale. Property prices will then crash. This group is the weakest link among private property owners.

You need to own a private property and live in it to be upper middle class. The top 20% own and live in a private property.