can you help to provide the threshold voltage of VSx in TPS650832?

Marvin,

These values are defined in the datasheet Table 6-1 in the 3rd column "Comparator Input". There it states the voltage and whether it is a logic input or an analog input. If it is an analog input the voltage defined in this table +/- 5% is the threshold for output going HIGH depending on the direction of the voltage change.
Threshold is +/-8% for output going LOW. Thus, there is 3% hysteresis on the +/-5% threshold value from the defined voltage in the table 6-1. See page 19 for threshold values.

If the table says "Logic Input" then the comparator is TTL logic, thresholds are defined in electrical specs on page 18.