"It might be revoked earlier if the situation improves," he told the AFP news agency.
The recommendation to prolong the state of emergency for another three months will be presented on Tuesday to the Thai cabinet.
Abhisit Vejjajiva, the Thai prime minister, has said previously that emergency rule would likely be lifted in many areas but not Bangkok, rejecting a call from the opposition for it to be revoked ahead of a parliamentary by-election in the capital due on July 25.
A red shirt leader detained on charges of terrorism during the unrest earlier this year is running in the Bangkok by-election as a candidate for the opposition Puea Thai Party.
In April, two months of mass protests by the red shirt movement calling for Abhisit to resign and call fresh elections, sparked outbreaks of violence that left 90 people dead, mostly civilians.
In response Abhisit invoked emergency rule in Bangkok on April 7, banning public gatherings of more than five people and giving broad powers to the police and military.
Human rights campaigners have voiced concerns that the government's use of the sweeping emergency powers lacks transparency and violates freedom of expression.
Enraged red shirt protesters went on a rampage of arson across central Bangkok after a deadly army crackdown ended their rally on May 19.
The unrest also spread outside the capital, particularly in the red shirt heartland in Thailand's impoverished northeast.