* Says only she understands depth of lawlessness in country
* Says she hopes for return of Crimea
* Ditches her hair-braid in image change (Adds background, quotes)
By Pavel Polityuk and Richard Balmforth
KIEV, March 27 (Reuters) - Ukrainian former prime minister Yulia Tymoshenko, released from jail last month after her arch-foe Viktor Yanukovich fled from power, said on Thursday she would run again for president in an election on May 25.
She also pledged to build a strong army and said she hoped to be able to recover Crimea from Russia, which annexed it last week.
The announcement by the flamboyant Tymoshenko set up a contest with boxer-turned-politician Vitaly Klitschko, who has also declared his candidacy, and other figures who have emerged to contend for top posts after four months of political turmoil.
"I plan to run for president," she told her first news conference since being released from jail a month ago. "None of the politicians understand the depth of lawlessness (in the country) and nobody wants to end it as desperately as I do," she said.
Tymoshenko, 53, a powerful speaker known in her heyday for her trademark peasant hair-braid, served twice as prime minister and ran for president in 2010, only to be narrowly beaten in a run-off vote by Yanukovich.
Yanukovich, her nemesis, subsequently launched a campaign against her and her allies, and she was jailed in 2011 for abuse of office linked to a gas deal she brokered with Russia in 2009.
She served two years of a seven-year term, mainly under prison guard in a hospital in Kharkiv, before being released when Yanukovich fled on Feb. 20 and was subsequently ousted by parliament.
She was wildly popular at the height of her power 10 years ago when she led tens of thousands on the streets of Kiev against an earlier bid for power by Yanukovich in what became known as the Orange Revolution.
But though there was sympathy from many people for her plight during her incarceration, many take the view that she was divisive and headstrong when in power.
Her time as prime minister was marked by infighting between her and then President Viktor Yushchenko which doomed the record of the 'orange' order in office and allowed Yanukovich to return to power.
When she was brought to the 'Maidan' - Independence Square - in late February to face the tens of thousands who had forced Yanukovich out after three months of violent turmoil in which more than 100 people had been killed, she met with a mixed response from people disenchanted with the political class as a whole.
Recent opinion polls measuring people's trust in today's leaders show her well behind Klitschko, a former world heavyweight boxer who has declared his intention to run, and confectionary oligarch Petro Poroshenko, an early and influential supporter of the 'Maidan' revolt who has yet to declare his intentions.
Tymoshenko appears now to have decided to re-brand herself possibly in an attempt to distance herself from an old image which could be used against her in the coming campaign.
On Thursday she eschewed her hair-braid and was carrying a stick, a reminder of the back trouble that plagued her in prison and for which she has had treatment in Berlin since being released.
"I must stand for president because I am the only person who has realistically shown how to end corruption in all spheres," she said.
And she went on to argue that, as someone born in the industrial east of the country, she was particularly suited to build a bridge with Russian-speakers there, many of whom are unhappy over the way Yanukovich was forced out of power.
"I can find words and arguments for my mother and that means for those who represent the east and live in the east," she said.
With an eye to Russia's annexation of Crimea, she said she would build a powerful security system and a strong army.
"I am convinced that I will be able to defend the country from aggression. I hold out a hope for the return of occupied Crimea," she said. (Writing by Richard Balmforth; Editing by Alessandra Prentice)
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