Thailand woke on Wednesday to confirmation that military leaders had staged an overnight coup.
Martial law has been declared, with large gatherings of people and critical news reporting banned.
The country's stock market, banks and schools will be closed on Wednesday, which has been declared a public holiday.
The coup leaders have said that regional army commanders will take charge of areas outside the capital, Bangkok.
Mr Thaksin's deputy and chief aide, Chidchai Vanasathidya, has been taken into army custody.
Army chief Gen Sonthi Boonyaratglin said in a TV address that the coup was necessary to unite the country.
For ordinary Thais, the next few days could be uncertain and uneasy.