Three Thai pro-democracy leaders in hospital

Scores of protesters, including several protest leaders, were arrested under emergency measures that were dropped a week ago after they backfired by drawing much bigger protests.

A pro-democracy activist attends a rally urging the release of protests leaders Panupong Jadnok, Panusaya Sithijirawattanakul and Parit Chiwarak. Source: AAP

Three prominent Thai pro-democracy leaders are in hospital after chaotic scenes outside a Bangkok police station as officers tried to slap them with further criminal charges.

A court on Friday ordered the release of Panupong "Mike" Jadnok, Panusaya "Rung" Sithijirawattanakul and Parit "Penguin" Chiwarak who have been in custody since mid-October on sedition charges - but police sought to question them over outstanding arrest warrants.

For months, protesters have staged almost daily rallies demanding reforms to the country's monarchy and for Prime Minister Prayut Chan-O-Cha - the former military chief who staged a 2014 coup - to resign.

The student-led demonstrations are also calling for a rewrite of the military-scripted constitution and an end to alleged government harassment of political opponents.

Panupong appeared to be unconscious as he was loaded into an ambulance outside the police station Friday night after being transported in a police van from jail.

Local media said he fainted after being subjected to a "chokehold" by plainclothes police.

Parit and Panusaya were allowed to mingle with about 300 supporters outside the station for several hours until police from Ayutthaya, 80 kilometres (50 miles) north of Bangkok arrived to question them in the early hours of Saturday morning.

"The iron bars can imprison the stars but not the starlight. In my heart, I still have faith in the people. The wind of change, the wind of democracy has arrived in Thailand," Parit told the crowd, who sang songs.

Tosaporn Sererak, a doctor and former lawmaker, was with the pair as they were loaded into an ambulance around 4:30am.

Parit Penguin Chiwarak, and Panusaya Rung Sithijirawattanakul raising up their three-finger salute with their supporters. Source: AAP

"After questioning, both Rung and Penguin were feeling weak and have been sent to hospital where they are expected to stay for two-three days," Tosaporn told AFP, adding Parit has shards of broken glass in his skin from a scuffle in a police van.

Panusaya had foot pain, he said.

Authorities will seek a court order to have them remanded in prison upon discharge from hospital.

Officers visited Panupong in hospital before 7:00 am on Saturday.