An opposition activist said Arisman Pongruengrong, who spearheaded Saturday's demonstrations, was taken away from his house early on Sunday by unidentified officials.
Police later confirmed Arisman's arrest.
On Saturday, leaders of the 10-member Association of Southeast Asian Nations(Asean) had to be evacuated by helicopter after protesters broke into the summit venue at the Thai beach resort of Pattaya.
The protesters breached police lines, smashing their way into the venue's media centre, while most of the leaders were having lunch at the adjacent Royal Cliff hotel.
Once in the media centre, the protesters paraded around with flags, blew whistles and horns, helped themselves to the snack buffet laid on for the journalists.
About 100 demonstrators got as far as the driveway of the hotel.
A group of rival blue shirt-clad protesters clashed, with the red shirts, throwing stones and smoke bombs at each other about five kilometres from the venue.
A Thai official said two or three people were injured in the clashes and there were reports of gun shots and an explosion.
The collapse of the summit puts more pressure on British-born Abhisit, who has pledged that his four-month-old government will heal years of political turmoil since Thaksin was ousted in a 2006 coup.
The abandoned summit - the biggest international gathering since the G20 summit in London earlier this month -grouped the Asean nations with China, Japan, South Korea, India, Australia and New Zealand.
"Yesterday was a truly shameful day for our country, which had its international image destroyed by the siege of the Asean venue in Pattaya and the embarrassing postponement of the forum," the Bangkok Post newspaper said in a front-page editorial on Sunday.
Protesters said they had run out of patience with Abhisit's refusal to bow to their demands for him to resign and hold new elections.
"The red shirts have been asking him to resign for four months and we decided that now was the time to push him," Pichet Sukjindatong, one of the protest leaders, said.
Officials did not say if or when the summit would resume - it had already been postponed and shifted to new venues several times in an attempt to dodge the protest threat.
|Protesters stormed the Asean summit venue on Saturday, forcing its cancellation [AFP]
Ban Ki-moon, the UN secretary-general, who had been due to attend the talks on Sunday, led expressions of regret.
"I hope for an early restoration of normalcy in Thailand and for the settlement of differences through dialogue and peaceful means," he said.
Thaksin's supporters say Abhisit, whose coalition government came to power four months ago, became prime minister illegitimately after a parliamentary stitch-up engineered by the army.
Four prime ministers in the last 15 months have failed to resolve Thailand's deep political rift which pits the military and business elite against a rural majority loyal to Thaksin.