I want to thread some small, fairly lightweight beads onto thread for a necklace. Can i use Gutermann sewing thread?

[SleepwalkingThroughLife]

Or do i need special thread? I want drapey thread, not stiff plastic thread.

You need beading cord and, preferably, a beading needle. That makes it much easier to get the beads on the cord. You need to see how big the holes in your beads are and get a suitable guage cord.

Have you thought about the kind of closure you want. If you want a lobster claw clasp or an Australian clasp, you will need to use clam shells and jump rings to attach the cord to the closure.
If you don't want the beads to crack or have the colour rubbed off through time (depending on what kind of bead you have), you need to put a small knot between each bead.
Apologies if I am try to teach my granny how to suck eggs😀

Chinese knotting cord might be what you need
We do macrame style semi precious beads and knot around them
You get it on eBay quite cheaply

This is what we use
You could try embroidery silks too

www.ebay.co.uk/itm/Purple-Nylon-Chinese-Knotting-Cord-0-8mm-15m-Length-E40-4/232833800265?hash=item3635f9d849:g:XH4AAOSw~jpbPIWY

Ah that's great, thank you both of you.

Dental floss can be useful .