Chamlong Srimuang, a key protest leader, told reporters the group would not try to march in the middle of the night.
"It's useless to move in the dark," Chamlong said as a growing crowd gathered at the prime minister's compound, which the protesters have occupied since August.
The alliance has previously marched at night.
"It will be D-Day. This will be our final push to bring down the government," Chokchuang Chutinaton, a 64-year-old protester, said, echoing Chamlong's rallying cry on Saturday for supporters to join the march.
The protesters have been attacked several times by small bombs and grenades, including a blast on Thursday that killed one person and wounded 29.
One of the eight people wounded by a grenade on Saturday died on Sunday.
No one has claimed responsibility for the attacks.
|Thaksin Shinawatra supporters staged a protest to counter that of the PAD [AFP]
Colonel Sansern Khaewkamnerd, an army spokesman, said police would be responsible for keeping the situation under control, but that 2,000 soldiers would be on standby in case police ask for help.
Police said 2,400 police would be stationed outside parliament, which is about 1km from the occupied prime minister's compound, Government House.
Hundreds of protesters dressed in yellow shirts streamed into the compound in the afternoon on Sunday, chanting slogans and shaking hand-shaped clappers that created a loud clacking rattle.
The mood was upbeat with the atmosphere of a street festival. Activists handed out flyers while people lined up for spicy rice and vegetable dishes or to buy T-shirts.
The government met with police and military officials on Sunday and they agreed to use "non-violent ways to deal with the PAD protesters", Natawut Saikau, a government spokesman, told the Associated Press news agency.
"Police and soldiers will not be armed with lethal weapons, only shields and batons," Natawut said.
The last time the protesters marched on parliament, street battles with police left two dead and hundreds wounded.
Nearly 100,000 protesters were involved in the October 7 rally, the biggest march so far and the country's worst political violence in more than a decade.