By Martin Petty

BANGKOK (Reuters) - The legal cases are piling up fast against Thai Prime Minister Yingluck Shinawatra and her party loyalists. If precedents are anything to go by, they should be more than a little worried.

During eight years of intermittent power struggles, Thailand's courts have become deeply politicized and their rulings haven't been kind to the Shinawatra family, whose parties and allies have been the country's undisputed electoral champions for more than a decade.

Since 2006, judges have ruled that two governing parties controlled by Yingluck's brother and former premier Thaksin Shinawatra be dissolved, $1.4 billion of the family's assets confiscated, two election wins annulled and nearly 150 politicians banned for five years, including a prime minister whose appearances in a TV cooking show cost him his job.

The prognosis doesn't look too good for Yingluck either. If five months of crippling street protests haven't been enough to contend with, her fate is now in the hands of Thailand's topsy-turvy, at times bewildering, checks and balances system.

"It's now a tense time for the prime minister. The protests have been a pain in the neck, but they have no real legitimacy under the law," said Jade Donavanik, a legal expert and Thai university law lecturer.

"The judicial issues, however - these are real cases and real threats."

Supporters of the Shinawatras say the courts have been tampered with by an establishment of oligarchs who are loathsome of populist, self-exiled Thaksin, but incapable of challenging him at the ballot box.

The pro-government camp calls this a "judicial coup" that's less likely to draw the international condemnation that comes with a military putsch, something Thailand has seen many of, most recently against Thaksin in 2006.

Legal cases involving Yingluck and her Puea Thai Party have been taken on with unusual frequency since the latest tumult exploded in November, the most active being the Constitutional Court, which on Wednesday accepted a new case against the prime minister, lodged by 27 senators who say she abused her power when she removed the national security chief back in 2011.

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OPPOSITION HOPING ONE CASE WILL STICK

But the same court on Wednesday threw out a complaint by a deputy prime minister against protesters for attempting to overthrow a democratically elected government, arguing it was a criminal issue and therefore not under its jurisdiction.

The court last month annulled a protest-disrupted February 2 election and shot down a major infrastructure spending plan aimed at attracting investment and reviving an ailing economy.

In November, its judges - several of whom had a hand in drafting the 2007 constitution - thwarted Puea Thai's attempt to scrap the system of appointing senators, ruling that a wholly elected legislature was too democratic and therefore unrepresentative of the minority.

Some 308 mostly Puea Thai politicians who supported the charter change bill, Yingluck among them, face disqualification if complaints against them are pursued by the courts.

Some political analysts say the street protests are unlikely to dislodge the government, so the opposition is piling on as many legal challenges as possible against Yingluck and Puea Thai, assuming at least one of cases will bring them down.

The case seen most likely to achieve that is the charge of dereliction of duty in overseeing a cash-draining rice subsidy scheme that brought Yingluck to power in the 2011 election, but incurred billions of dollars of losses.

The National Anti-Corruption Commission, a panel with a broad remit beyond graft-busting, is overseeing the case and now deciding whether Yingluck should face impeachment by the upper house Senate, a semi-appointed chamber that is Thailand's only legislative organ in the absence of a sitting parliament.

The commission, which includes several members known to have had an axe to grind with Thaksin, on Tuesday decided the former president of that parliament, Somsak Kiatsuranon, of Yingluck's Puea Thai Party, would face impeachment for seeking to change the way the Senate is comprised.

The Shinawatras' supporters have long cried foul about the courts, the backgrounds of the judges and what they say are their broad remits and interpretations of the laws.

Many have voiced suspicion about the contrastingly good fortune of the pro-establishment Democrat Party, the opposition that backs anti-government protesters and escaped dissolution twice in the three years, most recently in 2010, on a clerical technicality.

"It's clear there's double standards being used by our courts and everyone can see that," Deputy Prime Minister and Justice Minister Pongthep Thepkanchana told Reuters.

"What we want is a judicial system where everyone is equal ... only then can we have peace and democracy. If we did wrong, then punish us. But if others do wrong, then make sure they get punished too."

(Editing by Nick Macfie)