Government deputy spokeswoman Sunisa Lertpakawat said the ISA, which is due to expire at the end of this month, will be extended from May 1 through June 30 in Bangkok, Nonthaburi, Pathum Thani's Lad Lum Kaew district and Samut Prakan's Bangplee district.
The ISA extension came as political movements persist, while the public, she said, has been instigated to cause possible confrontations between opposing political factions and subsequent disorder.
Ms Sunisa said there would be some adjustment in the deployment of security personnel as the number of protesters in some areas has decreased.
Caretaker Deputy Prime Minister/Foreign Minister Surapong Tovichakchaikul said before the Cabinet meeting that the number of military deployed will be reduced to three or four thousand, but the number of police officers will be increased to monitor the situation.
Mr Surapong is chief advisor to the Centre for the Administration of Peace and Order (CAPO).
Meanwhile, the red shirt United Front for Democracy against Dictatorship (UDD) today said it cannot say if the mass protest set for May 6 on Aksa Road in Nakhon Pathom will be prolonged or not, but pledged that the move will be peaceful.
Key UDD leader Natthawut Saikua said it depends on the ruling of the Constitutional Court on caretaker Prime Minister Yingluck Shinawatra's allegedly unlawful transfer of National Security Council chief Thawil Pliensri.
He said the red shirts are ready to accept a court ruling against the caretaker if it is fair and reasonable although Ms Yingluck will have to stop performing her premiership duties.