No you can’t, you’d need a Global Pass. It is surely not more expensive than buying the One-country pass + tickets to the border.

Please note that there is a quota for passholders on Thalys trains, it can sell out weeks in advance (32€ seat reservation, one of the most expensive out there...). Check availability here : https://www.b-europe.com/EN/Booking/Pass#TravelWish

Alternatives :

• Thalys Paris - Brussels (27€, more availability) + hourly reservation-free IC afterwards
• TGV Paris - Lille (limited 10€ fare, then 20€) + IC trains across Belgium
• fully reservation-free via Maubeuge and Charleroi

TGV trains are very popular, especially if you’re heading south. Do not wait to book. There are always reservation-free alternatives but they take a lot longer. Check here (no quota) : https://travel.b-europe.com/Eurail-GE/en/booking-tgv#TravelWish

Do not hesitate for further questions :)