I wrote a blog post about visiting a food expo in Bangkok, mostly about looking into tea offerings there. It was probably what you'd expect, a little Ceylon here and there, only a bit of interesting Thai tea, some strange offering related to coffee brewing devices being used to make tea.
On the more general subject, expos are one way unusual products, or even completely common products, are presented and sold in Thailand. In some cases it's a good way to get specials not offered elsewhere, for goods like electronics, or for deals on travel vouchers. It's possible someone might find some tea or coffee they couldn't normally find, or more likely to see coffee maker options that don't come up, or better prices on those. Events are held in places like Queen Sirikit convention center or Impact, with this one at the latter.
The grocery stores here cover so much food range that it's hard to imagine what could be there that wouldn't be in them, and since the main theme (as I saw) wasn't about retail sales of imported Western goods the purpose of visiting might instead relate to specialty foods that aren't offered everywhere, different dried goods or gyozas or sausages, lots of things.
Vendors like Chang and Singha had large displays there but I'm not sure what new information they would communicate, maybe just more like a real-life interpretation of a commercial. Since this post is focused on tea, what I write a blog about, it really wouldn't do a lot of food scope justice though.
http://teaintheancientworld.blogspot.co … -expo.html