640 Adafruit Industries Conductive Thread, 2 Ply, 23M

This thread is 2 ply, a little thicker than every day polyester or cotton thread but still thin enough to be sewn by hand in medium-eye needles or with a sewing machine that can handle 'heavy' thread. Because it is strong and smooth, its ideal for any wearable/e-textile project. It also has fairly low resistivity, 16 ohms per foot so you can use it to drive LEDs and other electronic components that use under ~50mA.

• Measures 0.2mm thick
• 2 ply thread
• 1.3 ohm per inch