I heard about it once and now I wanted to try.
You can sew with embroidery (or crochet) cotton, but not the regular way, you wouldn't be able to thread the needle and if you were, the stitches wouldn't be created.
You must wind it to the bobbin as the lower thread.
The upper thread's tension must be adjusted not to make the fabric wring and not to be loose at the same time. You must sew at the wrong side.
I used the colour of the fabric at the upper thread, but of course you may use the same as the cotton or anything you want :-)
I don't make any knots in the end, I just pull the cotton down with a needle.
The result is quite satisfactory, regarding the small amount of effort it took:-)
These are my new cotton-decorated trousers:)
The last word - you shouldn't use this technique on very light fabrics, they could get deformed.