The rally was designed to show support for Prime Minister Somchai Wongsawat, who has appeared helpless in ending the crisis that has stranded up to 100,000 travelers, brought the key tourism industry to a virtual standstill and affected plane schedules worldwide.
Somchai has been forced to run the government out of the northern city of Chiang Mai because of fears for his safety in the capital.
Sunday's explosions hit Somchai's Bangkok office compound, which protesters seized in August and have held ever since, an anti-government television station, and a road near the main entrance to Bangkok's domestic airport, which the protesters are also occupying. At least 51 people were injured, including four seriously, officials said.
No one claimed responsibility, but Suriyasai Katasiya, a spokesman for the protest group, blamed the government.
The protesters, who call themselves the People's Alliance for Democracy, overran Suvarnabhumi airport, the country's main international gateway, last Tuesday. They ngkok. But authorities there were overwhelmed with hundreds of screaming and shoving passengers cramming into the small facility, trying to get their bags scanned through a single X-ray machine.
"It was terrible! There was pushing and shouting and we couldn't get in the front door," said Veena Banerjee of India, trying for the second day to get on a plane.
The Federation of Thai Industries has estimated the takeover of the airports is costing the country $57 million to $85 million a day. Some of its members have suggested they might not pay taxes to protest the standoff.
"The situation has gone from bad to worse, signaling that it (the government) is incompetent at ensuring peace and order," the Thai Chamber of Commerce said in a statement Saturday.
Some Thais are looking to the judiciary for a way out of the crisis. The Constitutional Court is expected to rule soon on whether three parties in the governing coalition including Somchai's People's Power Party committed electoral fraud.
If found guilty, the parties would be dissolved immediately, and executive members including Somchai would be barred from politics for five years.
Others are counting on the monarchy to end the standoff. Revered King Bhumibol Adulyadej, who has repeatedly brought calm in times of turbulence during his 62-year reign, will give his annual birthday-eve speech on Dec. 4.
"No one else can fix this. The country is so divided. The only uniting figure we have is the king. If he tells both sides to step back, they will," said 36-year-old coffee shop owner Natta Siritanond.