Q: What are the protests about?
Thailand has been rocked by years of often-violent demonstrations by rival protest movements.
The current anti-government demonstrations, led by senior opposition figures, are seeking an end to the "Thaksin system" -- the legacy of former prime minister Thaksin Shinawatra who was ousted in a coup in 2006 and lives in self-imposed exile.
The rallies were triggered by a controversial amnesty bill introduced by the ruling party which could have allowed Thaksin to return to Thailand without going to jail for a graft conviction that he contends was politically motivated.
The legislation was rejected by the upper house but the emboldened opposition Democrats and their street protest allies have increased their demands and are now calling for the government to be toppled.
The protesters accuse the government of Prime Minister Yingluck Shinawatra -- Thaksin's sister -- of corruption, an accusation also levelled against the opposition when it was in power.
Q: Who are the competing protest groups in Thailand?
The rival movements are the "Red Shirts", loyal to Thaksin, and their arch rivals the royalist "Yellow Shirts" who were once a major political force but are no longer active.
Yellow rallies have helped to eject Thaksin or his allies from power three times, while support from the Reds swept Yingluck to power in 2011 in the wake of a deadly military crackdown on their pro-Thaksin street protests.
The opposition protesters currently on the streets are a mixture of former Yellow Shirts, Democrat supporters, royalists, students, urban middle class and other Thaksin opponents.
Tens of thousands of Red Shirts have staged a rival protest in support of the government, accusing the opposition demonstrators of seeking to overthrow a democratically elected adminstration.
Q: What are the possible scenarios?
The government appears reluctant to use force to break up the protests. A military crackdown on the Red Shirt rallies by the previous government in 2010 left more than 90 civilians dead and nearly 1,900 wounded.
Yingluck's best hope is for the protests to end peacefully, possibly ahead of the revered king's birthday on December 5.
She could call a snap election, which many analysts believe her party would still win, albeit probably with a reduced majority in parliament.
But she cannot dissolve parliament until after the end of a no-confidence debate on Thursday that she is expected to easily survive.
The Red Shirts could also decide to step up their pro-government protests, raising the risk of clashes between rival political factions.
Q: Could the army or the courts intervene?
The possibility of military intervention constantly looms over Thailand, which has seen 18 actual or attempted coups since 1932, most recently in 2006 when royalist generals toppled Thaksin.
But the army has so far shown no sign that it is preparing to get involved.
The judiciary also has a record of intervening in politics, dissolving parties and banning their executives, and some observers believe corruption allegations against the ruling party could form the basis for another "judicial coup".
Revered King Bhumibol Adulyadej intervened during several political crises in the 1970s and 1990s but the 85-year-old monarch has been in ill-health for several years and rarely speaks in public.