BANGKOK - Thai lawmakers chose US-educated businesswoman Yingluck Shinawatra as the country's first female prime minister Friday, setting the stage for the 44-year-old political novice to take charge of a volatile nation that's been deeply divided since her brother was ousted in a 2006 coup.

Before Yingluck can officially assume the post, however, King Bhumibol Adulyadej must endorse her in a separate ceremony expected to take place as early as Friday evening.

The vote comes a month after Yingluck's Pheu Thai party swept the country's July 3 elections, winning an absolute majority of 265 seats in the 500-member lower house of Parliament. Since then, Pheu Thai has consolidated those gains, building alliances with smaller parties to form a 300-seat-strong coalition.

But Thailand's people remain split, and Yingluck will face the immediate challenge of keeping the country clear of the sometimes violent unrest it has witnessed since the army toppled her now-exiled brother, Thaksin Shinawatra.

Thailand's new Prime Minister Yingluck Shinawatra of the Puea Thai Party gestures to members of parliament moments after being elected as the country's 28th prime minister in parliament in Bangkok August 5, 2011. [Photo/Agencies]

To do so, she must navigate complex political terrain and find a delicate equilibrium between the army and the elite establishment on one side, and the so-called Red Shirt movement on the other.

Analysts say Pheu Thai's landslide victory last month boosted Thailand's prospects for stability in the short-term, but that honeymoon may only last a few months.

"To reinforce the stability of her government, Yingluck must find a way to work in harmony with the military and the conservative powers," said Siripan Nogsuan Sawasdee, a professor at Bangkok's Chulalongkorn University.

It won't be easy.

The party Yingluck heads is the latest incarnation of Thaksin's original Thai Rak Thai party, which swept elections twice before Thaksin was overthrown. Two pro-Thaksin prime ministers who followed were removed after hostile judicial rulings and parliamentary maneuvering that came as enraged "Yellow Shirt" demonstrators took to the streets, at one point shutting down both of Bangkok's international airports and stranding hundreds of thousands of travelers.

The Red Shirts have fought back, most recently by flooding downtown Bangkok in 2010 for two months in demonstrations that ended with more than 90 people dead and nearly 2,000 wounded - almost all of them protesters.

Yingluck now faces the daunting task of reconciling the nation. She must also prove she is not her brother's puppet, as critics claim, and deal with the controversial issue of his possible return from self-imposed exile.

Thaksin, now 62, has dominated Thai politics since his ouster, despite living in a luxury residence thousands of miles away in the desert city of Dubai to escape a two-year prison sentence for graft he says was politically motivated.

Thaksin's popularity was reaffirmed by the recent election, a point underlined by one of Pheu Thai's campaign slogans: "Thaksin thinks, Pheu Thai acts." But his return, possibly under a general amnesty, would enrage his opponents and could destabilize Thailand.