On 13 September 1957, Sarit handed Phibun the army's ultimatum.
The ultimatum, signed by 58 army officers, called for the resignation of the government.
The public was supportive of Sarit's ultimatum.

On 15 September, a public gathering assembled to protest Phibun and his government.
The crowd, which quickly grew in numbers, marched to Sarit's residence to show support for the army's demands.
As Sarit was not at home, the crowd broke into the government compound where they made speeches condemning the government.
The protesters later returned to Sarit's home where he was waiting to address them.
In his speech, Sarit said, "In the name of the army and deputies of the second category, I have conducted my activities based on popular will, and the interests of the people — your coming here gives me moral support to continue."

The following morning, Sarit and his army staged a coup d'etat.
In less than an hour, the army successfully captured strategic points with no resistance.
To identify themselves, Sarit's forces wore white arm bands as a sign of purity.
Following these developments, Phibun immediately fled the country and Phao was deported to Europe.
Thus began Sarit's rule.
On 13 September 1957, Sarit handed Phibun the army's ultimatum. The ultimatum, signed by 58 army officers, called for the resignation of the government. The public was supportive of Sarit's ultimatum.
On 15 September, a public gathering assembled to protest Phibun and his government. The crowd, which quickly grew in numbers, marched to Sarit's residence to show support for the army's demands. As Sarit was not at home, the crowd broke into the government compound where they made speeches condemning the government. The protesters later returned to Sarit's home where he was waiting to address them. In his speech, Sarit said, "In the name of the army and deputies of the second category, I have conducted my activities based on popular will, and the interests of the people — your coming here gives me moral support to continue."
The following morning, Sarit and his army staged a coup d'etat. In less than an hour, the army successfully captured strategic points with no resistance. To identify themselves, Sarit's forces wore white arm bands as a sign of purity. Following these developments, Phibun immediately fled the country and Phao was deported to Europe. Thus began Sarit's rule.
Sarit Thanarat