Gütterman Extra Strong Thread
Gütterman Extra Strong Thread is my go-to thread when topstitching anything but denim, although I usually use it on denim too.
It seems less difficult to use than regular top-stitching thread and it doesn't seem to clog my machine. It gives great stitch definition and, as the name suggests, is strong as anything. Use regular thread in your bobbin and a spool of this on top.
The colours available are the closest match to all of our fabrics. If you need any help choosing your colour, just ask.