Thailand is again on the verge of political turmoil. An ill-conceived amnesty bill pushed through the lower house of Parliament by Prime Minister Yingluck Shinawatra earlier this month brought many thousands of demonstrators for and against the government into the streets of Bangkok, putting the country’s fragile democracy in peril.

The amnesty bill proposes to pardon almost anyone facing almost any charge arising from the period of political crisis from 2004 to 2010 — ranging from those charged with ordering the killings of demonstrators by the army and police in 2010 to some 25,000 people charged with graft and tax evasion. The bill would allow former Prime Minister Thaksin Shinawatra, Ms. Yingluck’s brother, to return to Thailand from self-exile, grant him amnesty from a corruption verdict and restore part of his confiscated fortune.

Mr. Thaksin, ousted in 2006 by a military coup, continues to control the ruling Pheu Thai Party. Ms. Yingluck proved herself to be a mere proxy of her exiled brother by pushing the amnesty bill. The Bangkok establishment — the military, the business community and those around the royal court — fears and loathes Mr. Thaksin, who has support in the rural areas and among the poor. Soon after the demonstrations broke out, Ms. Yingluck backed down and all parties of the coalition government have vowed not to revive the bill. But the opposition led by the Democrat Party still wants to topple the government and continues to fan the street demonstrations.

This episode falls into a pattern in Thailand, with government transitions too often a result of mass demonstrations escalating into violence, then leading to a military coup. Since the founding of the Thai constitutional monarchy in 1932, there have been nearly 20 military coups and attempted coups; as many constitutions, charters and interim charters; and 25 amnesties, establishing a culture of political impunity where recklessness, corruption and even murder become the norm. In more recent years, the politically motivated Constitutional Court has at times moved to disband the ruling political party. The court is scheduled to make a ruling on Nov. 20, which could disband the Pheu Thai Party. Since 2006, the court has twice disbanded political parties under Mr. Thaksin’s control.