Police Commissioner Adul Saengsingkaew has ordered security to be beefed up to protect personnel at many independent organisations - including judges - following the Constitutional Court's nullification of the February 2 general election.
Police stations throughout the capital were told to pay more attention to the offices of the Constitutional Court, the Election Commission, the National Anti-Corruption Commission and other independent bodies, police spokesman Piya Uthayo said.
The red-shirts have accused independent organisations of conspiring to topple the caretaker government under Yingluck Shinawatra.
The Constitutional Court ruled on Friday that the February 2 election was unconstitutional, ending Yingluck's hope of using the poll to return to power.
The anti-graft body is set to begin impeachment proceedings against Yingluck and some of her ministers for negligence in not preventing corruption in the rice-pledging scheme.
Anti-government protest leader Suthep Thaugsuban said recently that he would call another big rally on Saturday to put more pressure on Yingluck to step down, paving the way for an unelected government and reforms amid moves to try to force the Shinawatra clan from politics.
Moves by independent bodies and anti-government protesters have angered red-shirt supporters of the government, who threatened to call a huge rally to "protect" the government and democracy in early April.
Piya said the chiefs of all police stations in Bangkok had to assign security officials to guard all judges and senior officials of independent organisations.
He said police had to set up a security grid in risky areas, mostly near the offices of key agencies and the homes of top officials.
All passing vehicles in the areas must be searched for weapons, explosives or materials that could be used for violence and mobile checkpoints should be set up 400m from "risky" areas.
However violence has not been confined to the capital.
Three bombs that exploded in Chiang Mai province on Friday night may be related to anti-government groups, according to Pichit Tamoon, leader of the Chiang Mai pro-government red shirt group.
The ruling Pheu Thai Party were upset by the Constitutional Court judgement, but it was welcomed by anti-government protesters.
Party spokesman Promphong Nopparit urged people to wear black starting today in protest over Suthep's group, which disrupted the poll last month.
"We should wear black until Suthep's group stop the election disruption to show that we don't agree with their idea to delay another election to have an unelected prime minister," he said.
Opposition Democrat deputy leader Ongart Klampaiboon said the next election should not be held until the government and protesters can make a compromise deal. He said there was no rush to call a new election.
In 2006, he said a new election was called six months after the court's judgement to nullify the April 2, 2006 election. This time concerned agencies should take their time in order to get agreement from all concerned parties.
But Ongart failed to mention that the election due to be held after the nullified poll from April 2, 2006 never happened, as the military staged a coup to oust the then-prime minister Thaksin Shinawatra from power.
Ongart declined to say whether his party would boycott the new election, as it did last month.
He said the party would call a meeting next Saturday, the same day Suthep has called a huge rally, to establish its political stance but said it would not be based on Suthep's protest.