Thailand's prime minister has rejected an ultimatum from the red-shirted protestors to dissolve Parliament, but the protestors have now vowed to splatter the seat of government with their own blood if their demands are not met.

Tens of thousands of red-shirted protestors staged a rally in Bangkok on Monday. They demanded Prime Minister Abhisit Vejjajiva dissolve Parliament and call new elections.

The demonstrators marshaled around the heavily defended 11th Infantry Regiment headquarters where Abhisit has been hunkered down in recent days. They marched back to their main encampment later in the afternoon.

Former Premier Thaksin Shinawatra communicated with his supporters via video phone.

Former Premier Thaksin Shinawatra said, "The patience and unity of people are the heart of success. Do not lose heart yet. Be patient, just a little bit more."

The Red Shirts say they are requesting that each protester donate between 10 to 100 cubic centimeters of blood to meet their first-stage goal of collecting more than one million cubic centimeters. They have threatened to spill the blood if their renewed demand is rejected by 6 pm on Tuesday.

Red shirts leader Weng Tojirakarn said, "As soon as you dissolve the parliament, we will go back home. Then we can prepare to vote in an election. We don't want to see any conflict of classes which might lead to a class war, or war between people which is not my intention."

That would require between 10,000 and 100,000 people - roughly the crowd's peak size - to donate. A Red Cross official have expressed concern over the hygiene of drawing blood from so many people and noted that such a large quantity "could save a lot of lives," if it weren't destined to be spilled.

The collection of blood from demonstrators is due to begin on Tuesday morning.