For the best result when sewing canvas, you need either a heavy-duty sewing machine or an industrial sewing machine capable of running heavy duty thread for canvas.
You might "get away with" using a lighter, standard-duty, light gauge thread when you sew canvas, but you can't really expect what you make to holdup and last if you do.
In the fabric store, or online store, look for heavy gauge thread. In the store, the coarse thread you need for sewing canvas should be with or at least near the upholstery, drapery, or canvas department.
Also, if you plan to use the canvas item you're making outside, look for UV protected thread, or it will rot away long before your canvas wears out.
One final tip for sewing with heavy gauge thread: Use a large gauge sewing machine needle.