Police have made no move to arrest the protest movement's ringleader, Suthep Thaugsuban, who is demanding the country be led by an unelected council until reforms can be implemented.
He's vowed that the protesters will thwart the polls through civil disobedience. Authorities have to tread carefully, as a crackdown would likely provoke greater violence and chaos.
The current tensions date back to 2006, when Yingluck's brother, former Prime Minister Thaksin Shinawatra, was toppled in a military coup.
The protesters accuse Yingluck of being a proxy for Thaksin, who lives in self-imposed exile to avoid jail time for a corruption conviction but still wields influence in the country.
Thaksin or his allies have won every election since 2001.
His supporters say he is disliked by Bangkok's elite because he has shifted power away from the traditional ruling class, which is represented in the current protest movement.
