I haven't looked, but it's unlikely you can get there on Thalys without a change of train to local in Belgium. It's all a matter of time and comfort. I've daytripped to Bruges from Antwerp, but I wouldn't do so from Amsterdam. (The Netherlands have lovely daytrips from Amsterdam, including Den Haag, Delft, Leiden, Amersfoort, Utrecht - and that's just the west area.) So I wouldn't combine the two countries unless I had enough days of vacation.
Local trains in Belgium are all unreserved and easy to ride (luggage can be cumbersome on the double-decker commuter cars you sometimes encounter.) You might save money with local Netherlands trains but I don't think you can spare the vacation time to sit on a long-distance train that isn't the fastest.
Note that I'm not suggesting that Bruges isn't a great visit. It's the distance from Amsterdam that's the problem. And you're missing out on Antwerp, Gent, Leuven, Brussels, Lier, and more. This is a section of Belgium that's as thick with great towns as the west coast of the Netherlands. Have you looked at the NMBS website, as well as the Thalys website? You can view many journeys without having to proceed to buy a ticket.
Another idea. If you haven't bought your air ticket yet, home-AMS/BRU-home may be the same prices as a round-trip.