Police in Bangkok clashed Thursday morning with protesters trying to disrupt preparations for elections early next year.
Around 2,000 protesters gathered outside a sports stadium where lots were being drawn to determine candidates' ballot sheet numbers for the February 2 general election.
The protesters threw rocks and fireworks as they tried to get into the stadium, prompting clashes that lasted several hours.
One policeman suffered a gunshot wound and two more were hurt by fireworks, Police Major General Piya Uthayo told dpa.
Thirty-two protesters were hurt by rubber bullets or teargas.
Outside the residence of Prime Minister Yingluck Shinawatra, hundreds of demonstrators gathered to demand her resignation.
Her opponents say she is a puppet for her brother Thaksin, who was deposed as prime minister in a 2006 military coup, and lives abroad to avoid a two-year jail term for abuse of power.
The protesters, drawn mainly from Bangkok's wealthy elite and middle classes, and opposition strongholds in the south, have demanded an appointed council to run the country before any election takes place.
Yingluck called the election - which she is expected to win - in response to the weeks of protests, and has called for a special reform council to be set up after the ballot, to draw up legal and constitutional reforms.
Not satisfied, protesters have vowed to sabotage the polls, and the country's main opposition Democrat Party has said it will boycott the vote.
Yingluck's Pheu Thai party remains hugely popular in the north and north-east of Thailand. Thaksin-backed parties have won the past five general elections.