Some of the fiercest clashes took place outside of Government House, where mobs had lobbed gasoline bombs at police, who fired back clouds of tear gas, rubber bullets and blasts from water cannons.
On Wednesday, Yingluck returned to her office at Government House to meet with Cabinet ministers and senior economic officials, Thai media reported.
She was scheduled to leave in the evening for the seaside town of Hua Hin, where the king will host official ceremonies for his birthday.
Protest leader Suthep Thaugsuban vowed to keep up the struggle to topple Yingluck and uproot the influence of her brother, former Prime Minister Thaksin Shinawatra, from Thai politics.
Thaksin was ousted in a 2006 military coup, and Yingluck's rivals have repeatedly accused her of being Thaksin's puppet.
Suthep said that after a Thursday truce, “our battle” will resume early Friday.
