Risk of more violence

Yingluck called the election in December to try to defuse the protests and since then has headed a caretaker government with limited powers. The violence and political paralysis has dented confidence, prompting cuts to economic growth forecasts.

Yingluck's Puea Thai Party had been expected to win but the main opposition Democrat Party threw in its lot with the protesters and has demanded electoral changes before any vote, seeking to reduce the influence of Thaksin. Parties led by or allied to him have won every election since 2001.

The protesters retreated this month to a Bangkok park and the battleground has moved from the streets to the courts. Yingluck faces a spate of legal challenges that could bring down her government, including a charge of dereliction of duty related to a disastrous rice-buying scheme.

Thaksin's "red shirt" supporters, who are strong in the north and northeast, are beginning to make militant noises, raising the prospect of more violence if Yingluck is forced out by the courts, the anti-corruption commission or by other means.

"Independent agencies are being quite obvious that they want to remove her and her entire cabinet to create a power vacuum, claim that elections can't be held and then nominate a prime minister of their choice," said Kan Yuenyong, a political analyst at the Siam Intelligence Unit.

"If they run with this plan, then the government's supporters will fight back and the next half of the year will be much worse than what we saw in the first half," he said.

The streets have been relatively calm since several big protest sites were shut at the start of March and a state of emergency was lifted on Wednesday.

However, police reported that three grenades exploded just before midnight on Thursday near the home of one of the Constitutional Court judges. One person was slightly injured.

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