BANGKOK, Thailand — Thaksin Shinawatra, who resigned last week as Thailand's prime minister after several months of street protests, once said that running this country was like making apple juice. You had to destroy some nice apples, but this was ultimately justified by the sweet taste of the juice.

Perhaps because he departed from office sooner than the quarter-century he felt he deserved, he has left behind a mess of political pith and pulp that has seriously damaged the country's political institutions and climate.

When he came to power in 2001, Thaksin promised new thinking and new policies. It soon became clear that this entailed a reversal of the trends of the 1990s — namely, vibrant news media, strong civil society, more public participation and wide-ranging reforms. Thaksin used the electronic media for government propaganda, abused critics, violated human rights and disdained democracy and the rule of law.

In short, he brought back the authoritarian strain in Thai politics that optimists hoped had been laid to rest.

He also made a mess of the 1997 Constitution, especially by undermining the bodies intended to check executive power. The integrity of the new Constitutional Court has been hopelessly damaged by its questionable judgments in Thaksin's favor. After a series of blatant interventions on behalf of Thaksin's party in the April 2 election, the Election Commission has become a laughingstock.

These manipulations of Thai institutions are of a piece with the misuse of state power for profit. On becoming prime minister, Thaksin transferred his stake in the Shin Corp., the telecommunications company that he founded, to his family. But in a culture where family business is the norm and the patriarch is the boss, this arrangement distanced him from the business by the width of the dining table. The family's holdings tripled in value in his five years of power.

He also seemed unable or unwilling to prevent his relatives and political allies from leveraging their proximity to the seat of power. The auditor general recently quipped that this government's major achievement was "making corruption legal." As a result, the quality of political life has slumped. Any hopes that Thai politics might attract office-seekers other than concession hunters and construction contractors have been sadly dashed.

What then needs to be done?

Reforming the Constitution must come first. It has made politics more stable by strengthening the prime minister, but it has failed in its aim to create effective checks and balances that keep the executive honest.

Next, the electronic media must be reformed and liberalized. For years, broadcast television provided no debate of current issues, with government-owned channels squelching coverage of bad news right up to the election. One of the first orders of business must be "de-cronyizing" a new regulatory board for broadcast media and allowing more radio and television channels free of state control.

More broadly, there must be a purge of the many former policemen — Thaksin was in the force before he turned to business — and corporate associates whom he appointed to important positions in state agencies.

Finally, Thaksin needs to be brought to account. Unless he and those who profited from his administration face full judicial scrutiny, political and business interests will continue to be blurred and corruption will thrive.

None of this will happen, however, unless the fractured political opposition can provide a real alternative. By offering rural Thais some effective schemes in healthcare and economic development, and by convincing ordinary people that they mattered, Thaksin has raised expectations that those who claim to provide a more democratic alternative must meet.

Pasuk Phongpaichit, a professor of economics at Chulalongkorn University, and Chris Baker are the authors of "Thaksin: The Business of Politics in Thailand."