The Red Shirts will continue to march in the streets after learning that Thailand Prime Minister Abhisit Vejjajiva has rejected  the protesters’ demands to dissolve the parliament and conduct a new round of elections. But the latest protest tactic promises to be “bloody”  as organizers announced that they will collect 1 million cubic centimeters of protesters’ blood, or about 264 gallons (1,000 liters) and will throw the blood at the Government House in Bangkok by Tuesday evening.
The Red Shirts were able to mobilize at least a hundred thousand people in the streets last Sunday prompting the government to deploy more than 50,000 security forces in the capital. The following video clip  shows a big assembly of Red Shirts last weekend
Why are the Red Shirts protesting in the streets? Marc Askew interviewed the rally participants and summarized their demands :
They agree that the parliament should be dissolved and new elections held so as to “return power to the people.”
They argue that the Thai press and media cannot be trusted to portray the red shirt cause accurately, in contrast to the foreign media, which they believe “knows what’s really going on” in the country viz-a-viz political power.
They utterly reject the reports that people are paid to attend major red shirt rallies, as related in the press and among their opponents.
Saiyasombut commends the Red Shirts for conducting peaceful rallies but rejects the “blood protest” 
So far, the fact the protests have been peaceful and no bigger problems (or even violence) have occurred can be counted as a success and confident boost for the Red Shirts. But now they risk to lose all the momentum for this more than questionable stunt. First, there is the logistic problem: how on earth are they going to get enough blood of 100,000 people in just one night?
Secondly is a medical one: how are they going to get enough clean needles? The Thai Red Cross has refused to help, pointing out medical consequences of improper use.
And finally the question is: what do they want to achieve with this? Unless they want to deliberately create a big hygienic mess I don’t see anything being solved here!
Siam Report warns the Red Shirts that the “blood protest” would erode the group’s credibility 
…the reds shirts have thus far had a successful rally. They didn't reach a million people and no House dissolution, but at least 100,000 turned up and the protest was conducted in a peaceful manner. However, if the red leaders decide to go through with this symbolic blood splattering stunt, you can be sure that it will be received very poorly internationally. Such a stunt is perfect ammunition for the anti-red media, and really to any observer, it is an illegal act of vandalism and something a teenager would do.
Jon Dent participated in the March 15 rally and blogged about what he witnessed :
Walking towards the main stage, we saw groups of people walking while others sought shade from the mid-day sun. There were signs in English (“Democracy Now”) and signs in Thai (“We will die for Democracy”). There were stalls selling red shirts, anti-government literature and CDs, and of course Pad Thai.
I met a group of nurses and doctors volunteering at one of the many first aid stations along the protest route. They asked not to be identified since their hospitals told them not to help the Red Shirts. Nevertheless, they came anyways “to help the people, and because our hearts are Red.”
The Nation's State, another rally participant, is elated by the warm support  of Bangkok residents
Notable were the crowds of people gathered on the streets cheering for the reds.
They were Bangkok residents coming out to great and support the reds. Many were waving anything red that they had in their homes or work. I saw red bed sheets and red coffee mugs among other things.
Also notable were the police which came out to wave and some even sported red.
The mood was boisterous, like a party really, and the reds certainly scored a psychological victory by showing residents that there are far more protesters than reported in the media.
Nganadeeleg criticizes media bias  in reporting the rallies
I'm pleased that there has been no real violence to date, and it seems both the government and protesters have learned from the past.
(also more people have camera's at hand now so hopefully any actions by agent provocateur's will quickly be able to be seen as such).
My biggest complaint regarding the media coverage is that most are taking a very short term view and cannot see the wood for the trees.
Hungry guide to food and travel maintains a non-political blog but manages to write about the Red Shirts by featuring the exotic food items  sold in the rally sites.
Going to rally is not fun for those who has nothing to do with it, but it created lots of jobs and profits for some people, especially people who sell food. Some of them just come specially for rally, and some who usually are nearby, simply change the location just to show their support.
photo_journ : #redshirt trucks now playing protest/battle type tunes. Still attracting wide public support
photo_journ :If the reception the #redshirt convoy is getting is indicative of an election vote the Abhisit gov. is finished
RobinThailand : People on the street passing us food and water as we move down in the #redmarch.
newley : #redmarch protesters chanting, cheering, and throwing empty plastic water bottles into army compound.
legalnomads : @arzupancic No no – I didn't wear any red shirt. Was just there taking pictures – in green or purple or something neutral.
tulsathit : We've also learned that an unknown number of protesters headed for 11 regiment HQ and never came back. They simply went home.
The last tweet is good news for the government. It means the number of protesters are going down. BangkokDan believes the Red Shirts have failed 
The so far biggest show of force on Sunday with many sightseers and curious onlookers on Rajdamnoen was a sweet Pyrrhic victory before reality set in on Monday morning when the dancing and chanting solidarity started marching. Many of them knowing, this march actually leads to nowhere. They barely reached the 11th Infantry Regiment, the ultimatum passed – now the search for blood started. And many protesters, already packed, simply went home.
Nirmal Ghosh  is not sure whether the Red Shirts can sustain the protest momentum
The Red shirts have definitely made a statement today, but will it be enough to force political change? The government has played its cards well, not being drawn into a fight. Yet the grenade blasts show that the situation still hangs in the balance.
There is still no telling how many Red shirts can stay on the streets and for how long….
Many Red Shirts are supporters of ousted Prime Minister Thaksin Shinawatra but not all of them are fans of the fugitive leader who was recently found guilty by the court of corruption charges. Thaksin is now in Europe but he has been successfully addressing the rallyists through phone-in interviews. Jon Russell cites the strong social media presence  of Thaksin’s team
Thaksin’s strong social media presence on the web allows the public – including his supporters – to find information and opinions straight from him rather than reading through the media.
Social media gives Thaksin a free platform to air his opinions and views whilst allowing him to maintain contact with those who can longer see him in person. For his supporters, his social media presences allows them to stay close to his view and opinions which are accessible any time.
Rally photos  are also available at Legal Nomads.