OK, so red shirts or the (UDD)United Front for Democracy against Dictatorship and the (DAAD), support Thaksin Shinawatra who is in self imposed political exile after the coup that removed him from office in 2006. The groups are mostly comprised of folk from the north and northeast of Thailand who believe the present government was illegally created after the coup and the ultimate forced disbandment of Thaskin's political party.
The whole political thing in Thailand is very confusing but non threatening to foreigners and easy to ignore. Equally the start up of the protest I stumbled into was populated by very non threatening folks and it seemed that what ever the political ramifications, the McDonald's in the photo was doing a booming business.
Seems to be more settled (12/21/2010) now as the government mandated Center for the Resolution of the Emergency Situation (CRS) is proposing the lifting of the governments emergency decree. However, many of the red shirts issues have yet to be resolved, so we will see.