Originally Posted by Calusin

This is indeed the high speed train (Thalys). Please be aware the high speed train is more strict than the slower train. For instance, you MUST travel on the selected train and time.

Other rules for your fare (Semi-Flexible):
Exchange conditions: Exchangeable once until the day before the departure.
Refund Conditions: 50% refund if cancelled before the departure (in your departure station until 1 hour after the departure). No refund if cancelled after the departure.

If you want you are able to use your Thalys ticket for the journey Brussels Midi/South to Brussels Central Station.