Supporters of Thailand's now outlawed Thai Rak Thai party have held protests in the capital Bangkok - but the rally was smaller than expected.
Thaksin supporters and anti-coup activists attended the protest
More than 1,000 demonstrators wearing yellow headbands called for an end to the military leadership that came to power after a coup last September.
Security has been high since a court on Wednesday found Thai Rak Thai guilty of electoral violations last year.
The party was banned and its leaders barred from politics for five years.
The same court cleared the country's other main political party, the Democrats, of similar charges of election fraud.
Thai Rak Thai leaders condemned the outcome as unfair but have urged people to accept it.
The party's founder, Thaksin Shinawatra - who was prime minister until he was ousted in the coup - urged "everyone to stay calm and don't make any moves".
State of emergency
Hundreds of police - including bomb squad teams and police dogs - were deployed around Bangkok ahead of the demonstration.
Security officials had feared thousands of people could descend on the capital following Wednesday's verdict.
But it was a relatively small crowd that gathered in central Bangkok on Thursday afternoon to register their opposition to the post-coup leadership.
"Junta, get out!" cried the protesters, many of whom cheered when Mr Thaksin's name was shouted out.
Thai Rak Thai party official Veera Musigapong - who is among 111 leading party members including Mr Thaksin to be banned from politics for the next five years - was among the crowd.
"As someone who was personally affected, I am not accepting the decision of the tribunal which was set up by the coup leaders and their illegitimate power," he said.
Thailand's leaders had been braced for unrest this week, putting thousands of troops on stand-by and setting up checkpoints into and out of the capital.
The measures were boosted following the verdict, and army chief Sonthi Boonyaratglin said a few "hardcore" allies of Mr Thaksin were being specifically monitored.
"Security measures have been stepped up since last night and will gradually be increased," he told the AFP news agency. "The measures will be in place for a long time".
Interim Prime Minister Surayud Chalanont had warned he would impose a state of emergency if violence broke out.
In a day of drama on Wednesday, a constitutional tribunal found Thai Rak Thai guilty of malpractice during the April 2006 electoral campaign.
Announcing their verdict in a heavily-guarded Bangkok courtroom, after hours of suspense, the panel of judges ruled that the party should be disbanded and its leaders banned from office.
Earlier, they ruled that the Democrats - Thailand's oldest political party - had not maligned Thai Rak Thai in the same elections and would not have to disband.
Following the malpractice allegations, the April 2006 elections were annulled. Prime Minister Thaksin was ousted by the coup a few months later.
Despite allegations of corruption that surrounded Mr Thaksin during his time in office, both he and Thai Rak Thai still retain widespread popularity, especially in rural areas.
The military leadership has promised new elections and a constitution by the end of this year.
But frustration with the interim government has been growing and the economy is struggling.