Columns of military and police units who had rushed to protect the hotel and convention center on Friday could not contain the thousands of protesters who swarmed the streets of this beach resort, about 90 miles east of Bangkok.

Image A member of the Thai government security watched the protesters approached. Credit... Wong Maye-E/Associated Press

“I wish to assure the safety of the leaders,” said Mr. Panitan, who said that some leaders had been advised to stay in their hotel rooms.

Mr. Panitan also said several protesters were injured in clashes early Saturday between the protesters and pro-government demonstrators.

Protesters made their way past the gates of the convention center, and a small delegation of their leaders entered the meeting venue. The police were trying to talk them into leaving, Mr. Panitan said. “If that doesn’t work we will take other measures,” he said.

The disturbance offered leaders a close-up look at the political discord that is wrenching Thailand, some of it fueled by the economic crisis. Bangkok has been the scene of huge demonstrations against the prime minister in recent days.