Hello
I googled this because I bought this soundbar 3 weeks ago and want to mount the rear speakers on stands. It wasn't M6 or a metric thread.
If you search for "samsung swa-9500s thread size" you will find:
Notes for Wall Mounting the Surround Speakers
- Surround Speaker wall mounts must be able to support more
than 8.0 kg.
- Hole size : 1/4 - 20 UNC threaded insert
So 1/4 inch screws. I ordered some on the net; about $4, including postage. Let's see what comes and if it fits.