The news sites are reporting tanks in the streets of Bangkok and rumors of a military coup attempt.
Thailand has long been the most stable country in SE Asia, but has been subject to coups in the past. This is VERY interesting from an academic standpoint, but it's MUCH too early to forecast the impact on the region.
UPDATE 11:08 CT: Prime Minister Thaksin Shinawatra is in NY at the UN today. He's declared a state of emergency. It can't be too terrible, however - he's leaving for home on Thurs, which is a day earlier than planned. If things were in total chaos, you sorta think he'd bail from the UN right away.
UPDATE 11:34 CT: The PM is addressing the UN today, rather than tomorrow. No word on when he's going home. I think the earlier article got it garbled.
Also, it appears certain that the military is taking charge. However, there are two (at least) factions within the military, one sympathetic to the PM and one opposed, and it's not clear which faction has acted. Things are liable to get really interesting when PM Thaksin attempts to return to the country