Ok, just finished my first game as the Thais. It was a lot of fun! Thailand is somewhat unusual in that you can't (okay, maybe just I can't) become a real A+ superpower but you can absolutely stay competitive. To me, that's a positive; it's nice that you're not just gonna steamroll over everybody but at the same time you're not an absolute backward weakling. Strikes me as a nice balance.
Technologically I was behind most of the Euros most of the time. Germany and Russia were well beyond me, with France a little ahead. I was about the same as England, Spain, and Portugal but the first 2 of those were having major issues and Portugal never seems to excel past the Renaissance, which I guess is intentional. I ended up about on par with China and a bit ahead of Japan, the Mughals, and Iran.
The UHVs were interesting enough. It didn't seem like a huge challenge to get enough open borders agreements, really just a matter of getting to Optics in time to get a few Caravels out toward Europe. Making Ayutthaya the biggest city was a bit of a nail-biter. It wasn't that I didn't have the food, happiness, or health, but I was in a plague for most of the 1600's so I really only had a couple of turns to recover. Ended up size 16, just barely enough. The last goal was only possible due to the English deciding to disband most of their Indian stacks after they captured the cities. Oddly, the English didn't manage to get their conquerors until the 1840's, and the Dutch not at all, though that was probably due to their problems at home. Just so I know, are Indonesia or the Philippines included in "South Asia" for the Thai UHV? That last goal would have been a beast if I had also had to get rid of them. As it was I kicked the last Frenchman out of India in 1896 and collected my win 2 turns later.