"Today, we see blood with our eyes. We will fight," said top protest leader Sondhi Limthongkul. "At this moment, there is no way we will negotiate."
The group is demanding the resignation of the government, which it accuses of being a puppet of former Prime Minister Thaksin Shinawatra, who was ousted by a 2006 military coup and fled overseas to escape corruption charges. Current Prime Minister Somchai Wongsawat is Thaksin's brother-in-law.
The capital remains cut off from all civilian air traffic, stranding thousands of travelers and dealing a severe blow to the economy and tourism industry.
More protesters arrived at the airport in cars and buses despite road blocks set up by police, boosting their number to several thousand. One of the main elevated roads into the airport is controlled by the alliance's guards who are manning their own checkpoint.
Police, many in full riot gear, also had a much more visible presence, guarding an airport hotel and airport management offices, and assembling in a nearby administrative building. There appeared to be several hundred in the area.
The government on Thursday declared a state of emergency at Suvarnabhumi and at the smaller Don Muang domestic airport - also occupied by demonstrators - but has not taken any further firm steps. Its failure to end the illegal airport closures has led to calls in the media for Somchai to step down, even from those who oppose the protesters.
In a brief televised speech Friday night, Somchai gave no clue as to when the deadlock might be resolved.
"Do not be concerned. The security forces will use peaceful means," he said. "There will be negotiations and whatever else which is appropriate in the situation."
Government spokesman Nattawut Sai-Kua said National Police Chief Gen. Pacharawat Wongsuwan was demoted to an inactive post in the prime minister's office.
Nattawut declined to comment on the order, issued by Somchai.
It was not clear if Pacharawat was removed because police failed to evict the protesters, or because he apparently made no attempt to negotiate a peaceful end to the crisis, as the government had asked.
Many of the demonstrators were defiant, and said they did not fear if police attempted to disperse the crowd.
"Even though they are going to come here, it doesn't matter.
They can arrest us but we will come back again," said Vichai Hanvivatpong, 40, a protester inside the terminal.
He said he did not think the group was doing the right thing but "we have no choice. If you go for something big, you have to sacrifice something."
The airport takeover capped months of demonstrations which took a dramatic turn when the protest alliance seized the prime minister's office three months ago, virtually paralyzing the government.
Since then Somchai had been working out of the former VIP lounge at Don Muang airport, but the airport siege forced him to move his government to the northern city of Chiang Mai.
The lack of use of force by the government and the firing of the police chief have raised doubts about whether Somchai has the support of the police and the army, a powerful institution that has traditionally played a key role in the country's politics.
Army commander Gen. Anupong Paochinda has so far been publicly neutral in the political turmoil. He demanded protesters leave the airports and urged Somchai to call new elections, triggering speculation of a military coup.
The political crisis has battered the stock market, spooked foreign investors and dealt a serious blow to the tourism industry.
The Bangkok Post newspaper quoted experts as saying the damage from the airport shutdown could range between $3.7 billion and $6 billion if the standoff extends to December. The meeting and convention business has already suffered $310 million in losses, it said.
