The junta in January lifted martial law in 41 out of 76 provinces including Bangkok, but it remains in force in 35 other provinces, including Thaksin's northern stronghold and the country's restive Muslim-majority south.
The government is likely to lift martial law in eight provinces next week, he added.
'Martial law will remain in force in 27 provinces, but is not aimed at obstructing political activities. It is to ensure national security,' Sonthi said.
Political parties and pro-democracy groups have urged the junta to lift martial law, warning that losers in the elections could cite the military restrictions to challenge the outcome of the vote.