BANGKOK (Reuters) - The Thai army took control of Bangkok on Tuesday without a shot being fired, dismissed Prime Minister Thaksin Shinawatra, revoked the constitution and promised a swift return to democracy after political reforms.

Thaksin telephoned a Thai television station from New York to announce a state of emergency in an apparent attempt to head off the coup. A government spokesman with him at the United Nations said the army could not succeed and "we"re in control."

But tanks and troops took over Government House in Thailand"s first coup in 15 years and a coup spokesman said the army and police were in control of the capital and surrounding provinces.

Armored vehicles and soldiers took up position on many street corners, but life in most of Bangkok continued much as usual with traffic moving through rain drenched streets and the airport operating normally.

The seizure would be temporary and power "returned to the people" soon, retired Lieutenant-General Prapart Sakuntanak said on all Thai television channels.

Foreign news channels, including CNN and the BBC, were cut off.

The army told all soldiers to report to base and banned unauthorized troop movements, suggesting the military leadership was worried that Thaksin loyalists in the armed forces might attempt a counter-coup.

Prapart said the armed forces and police had set up a body to decide on political reforms, ousting billionaire telecoms tycoon Thaksin in the midst of a political crisis stemming from accusations he had subverted Thailand"s 74-year-old democracy.

"RAMPANT CORRUPTION"

"Never in Thai history have the people been so divided," Prapart said.

"The majority of people had become suspicious of this administration, which is running the country through rampant corruption," he added.

"Independent bodies have been interfered with so much they could not perform in line within the spirit of the constitution."

Weerasak Kohsurat, a deputy minister in a previous government, said he believed royal adviser Sumate Tantivejakul would steer the political reform process.

Elections would be called when it was done and Thaksin, Thailand"s longest serving elected prime minister, would be allowed to take part, he said.

Thaksin himself was scheduled to address the opening of the U.N. General Assembly at 2300 GMT on Tuesday, and it was not immediately clear when he would return to Bangkok.

After mass street protests against him in Bangkok, Thaksin, winner of two election landslides, called a snap poll in April, hoping his firm rural following would counter his metropolitan opponents.

However, opposition parties argued he had skewed neutral bodies such as the Election Commission in his favor and boycotted the poll. That rendered the election result invalid.

Thaksin"s Thai Rak Thai (Thais Love Thais) party was expected to win a re-run tentatively scheduled for late November, increasing pressure on his opponents in the military and the old establishment to resort to removing him by force.

"There is no other means to solve the political deadlock," said a former senior official close to the top military brass. "It"s been almost a year that the country has no democracy, no legitimate government to run the country.

"I"ve told foreign diplomats Thailand may need to take a step backward, if they think a coup will, in order to leap forward."

BAHT PLUNGES

The Thai baht, one of Asia"s strongest currencies this year, suffered its biggest fall in three years within hours of the coup.

But the Stock Exchange announced it would open as usual on Wednesday, although it clearly expected investors to sell, saying it would halt trading if the main index fell more than 10 percent.

News of the coup also helped lift the dollar and U.S. Treasuries as some investors ducked into safe havens.

In his television statement, Thaksin ordered troops not to "move illegally" and told army commander-in-chief Sonthi Boonyaratglin to report to acting Prime Minister Chidchai Vanasatidya.

He also ordered Armed Forces Supreme Commander Ruangroj Mahasaranond to implement the emergency order.

The transmission stopped after 10 minutes while he was still talking.