the other non-Thalys route would be to take a regional train from Brussels to Lille-Flandres and then hook up with TGVs to Gare du Nord in Paris - could be a bit quicker than the CDG route and it seems little problem for passholders getting on Lille to Paris hourly or so TGVs IME - an option to keep in mind if you have problems getting on TGVs to CDG (and these TGVs go much less frequent than from Lille to Paris.

and a third non-Thalys option would be take an IC train Amsterdam to Antwerp - change for an IC train to Bruges - spend a few hours in this lovely city that is the consensus for the average tourist the top city in Belgium and then go via regional train to Lille-Flandres and onto Paris-Nord.

Ideally this route stay overnight in Bruges and make it too much shorter train days.