This is a theme I've been working on for a few years, related to living in Bangkok, but I don't think I've ever written about the general subject.
This started from a Facebook discussion, so I worked backwards from recommending a few favorite vendors there to add more about the range of versions from each country (Myanmar, Thailand, Laos, and Vietnam). It doesn't get far with saying versions from a certain country are a certain way, because it doesn't really work like that.
For example, I'd thought Myanmar sheng was more bitter than average, and many are like that, but the last version I tried was moderate and very well balanced. Bitterness isn't necessarily a bad thing, and can work well at different levels, it just depends. Here's that link:
http://teaintheancientworld.blogspot.co ... -asia.html
I'll ramble a little more, but really it's redundant, since I could only go into the scope there, a page or so of text worth. It lists some favorite vendors that provide sheng pu'er-like teas from those countries, and to some extent shu as well, although not nearly as much. Those include Tea Side and Lamphang Tea (Thailand), Hatvala (Vietnam), Kokang (Myanmar), and Kinnari and Laos Tea (Laos).
There are other sources; it mentions in passing that I've tried great Myanmar shu from Moychay too, or that Farmerleaf had been involved with economic development work and sales of Laos tea versions. I didn't mention trying a King Tea Mall Laos sheng version that was nice, but then this isn't a summary of every vendor or version I've ever encountered, more an overview, hitting some main points and best sources.
In the past the two main points of appeal related to trying something novel and buying tea that may be priced lower than typical, equivalent-quality versions from Yunnan. To some extent those differences are flattening back out, or maybe there is no difference in some cases now. Individual vendors build up customer base and demand and then their prices tend to drift up to a higher market-value equilibrium.
All of those cases related to a lot of individual tea reviews (overly wordy, detailed descriptions), but I also didn't mention that many links in that post, or even emphasize that point. It must be clear from the post but not in detailed form. Two friends have been passing on a lot of great sample versions from Laos and Vietnam over the past year or so too (Somnuc from Laos and Huyen from Vietnam), but the post doesn't mention that.