The AMANN Group
Among the most commonly use Amann product is their Rasant range of thread but they also make a wide variety of thread types from embroidery to industrial thread.
From their web site you should be able to set your preferred language and find out where to buy their products in your own country.
http://www.amann.com/en (http://www.amann.com/en)
Coats Group
Coats are an old English company that have been making thread since 1755 and are the largest thread manufacturer in the world.
Well known products are Coats Astra that is used in both sewing machines and overlockers. They also make GRAMAX which is a specialised overlocker looper thread for fine garments and stretchwear.
http://www.coatsindustrial.com/en (http://www.coatsindustrial.com/en)
THREADS (India) Limited
Part of the LOHAI GROUP
A manufacturer of a wide range of thread types for clothing and industrial tasks.
http://www.threadsindia.com/
Gütermann
A German manufacturer of many high quality and specialised thread types.
https://www.guetermann.com/
Regarding Coats Astra I am lucky to have a supply of it from my local cloth market, just 40 cents a reel or 3,50 euros for ten. It's one of the best quality threads for its price
Sorry, I had a typo in the title. I used to use Coats Astra for my main overlocker loopers but recently switch to Rasant as its a bit tighter. This has left me with a reasonable number of 5000 metre cones of black Astra which I now use as sewing thread in my straight sewer. Gives a nice neat and tight finish to normal woven fabrics.
Just adding to this... I've really struggled to find someone who could sell me shade cards for Gutermann threads, but I have finally succeeded with William Gee (https://www.williamgee.co.uk/). You need to send them an enquiry via the form here (https://www.williamgee.co.uk/shade-cards/), then they will send you an email with links to purchase. The Mara shade card is currently £10.00, the Sew-All shade card is £5.00, and shipping is free.
Here is a problem that I have.
My Juki twin needle needs s and z spun threads. I have also discussed the s and z threads with peterle before, but I have not found anyone else who knows anything about buying or selling the different types.
Can anyone say where to look for this distinction?
G
I bought my Gütermann Mara thread chart from Wawak. I think I bought a color chart for Sew-All from Minerva Crafts years ago.