Just got schooled a week or so ago in a local Asian market. There were well over a dozen options from a lot of countries. In general Thai sauce is the lightest, followed by Lao, VN, and Cambodia. The strongest comes from the Philippines.
There is a huge range in quality and it ferments for 6 months to years in jars or barrels, packed in salt.
I picked up a Thai and a Philippine example. They are very different. I have been using it for a very long time but had no idea how important it actually is.