If I could jump in here, and at the same time maybe get some more readers for my poor neglected journal...

I had some first-hand experience with the PAD and DAAD during
our two-week vacation in the Bangkok area in the latter half of November 2008. If you don't care to read through the entire journal, jump to the last three entries, starting with
post #12, titled "Hey, Go Coup in Someone Else's Ear" - which deal with the escalation of tensions and our escape from the country.
We stayed with family there, and while I had been following the political unrest closely via
the U.S. State Department's travel advisory site and the international news outlets over most of the year preceding our visit, we could never have predicted that
the PAD mob would take over both major Bangkok airports just a few days before our scheduled return to the US, effectively taking us and some 100,000 other travelers hostage.
Because we were staying with locals who were hooked into an on-the-ball network of family and friends, we were able to get out of the country via Chiang Mai, actually a day ahead of our intended departure - but it was no less dangerous, no less nerve-wracking and, obviously, no less a waste of the latter half of our visit.
What struck me was that the locals we talked to, from family to friends to random strangers,
were all angry and disgusted at both the yellowshirted PAD and the redshirted DAAD - to which they referred as simply "the mobs." The distinct impression was that the good, decent majority of Thai people want nothing to do with the collectivist mobs and retain as deep a respect for the Thai constitution and the rule of law as do the good, decent majority of Americans do theirs. But as is usually the case, the fanatical thugs get the press, and because they can get press, they labor under the delusion that publicity somehow imbues their criminality with a patina of justice and right. And yes, shutting down airports and stranding travelers, for whatever reason, is indeed a species of kidnapping, therefore a crime.
I don't claim to have an extensive grasp of the intricacies of Thai politics, but from what the family who put us up told us, what I've been able to gather from articles on the subject, and from what I know of philosophy and politics in general, the only significant difference between the two mobs is superficial - the PAD mob victimizes innocent bystanders intentionally, gleefully and without a second thought, while the DAAD mob generally limits itself to victimizing PAD adherents and anyone unlucky enough to get caught in the crossfire. On core philosophy they're virtually identical in their disregard for individual rights and for the rule of law, and in their embrace of collectivist policy.
One can only hope that voices of reason will arise within Thailand and demand that all parties respect the results of elections whether win or lose, and discontinue the recourse to brute force to achieve momentary political gain. This mob group-think mentality is only hurting the whole of Thailand and its people, to say nothing of international travelers.
To anyone planning on a Thailand trip, I'd advise just keeping close tabs on the State Dept. site and international news, but to be ready for anything and keep your eyes wide open when you get there. If you know Thai citizens or resident expats there, so much the better.
Generally if you stay away from any and all demonstrations and from government complexes, the only real danger you'll be in is the danger of being trapped there for an indefinite period. It's a nation bordered by countries that are generally even more dangerous than the internal demonstrations, also a country that has a relatively small number of international airports - which means it doesn't take much for international travel to be shut down. If you have the wherewithal to sit tight and wait it out, these Thai political storms generally blow themselves out in time. Most of us have family and jobs (or school) and other pressing obligations to get back to though, so plan accordingly.
My $.02 worth. I now yield the soapbox to...