To suppleement the link that yk has provided, here are additional links from the Belgian site. There is limited one-train servcice (no change involved):

http://www.b-rail.be/internat/E/dest....html#Oostende

Scroll down to the bottom for the Oostende > Paris Nord schedule. As you can see, there is only one direct train per day except on Saturdays (early morning departure on Mon-Sat, afternoon departure Sat-Sun only).

Any other times of day, you'd go into Brussels Midi and change.


To see fares:

http://www.b-rail.be/internat/E/dest...ris_fares.html