As the US embassy in Bangkok recommended residents stockpile two weeks of cash, food and water, army chief Prayuth Chan-ocha said he was concerned about the possibility of violent clashes and admitted he does not see a solution to end Thailand's crisis.
But General Prayuth asked the media to stop asking him if the powerful military, which has intervened to overthrow governments in the past, plans to stage a coup.
''A coup is not a topic that we should be talking about every day . . . I don't know what the solution is but we soldiers will do our best to ensure safety for the people,'' he said.
Earlier General Prayuth refused to rule out a coup.
Tens of thousands of protesters plan to erect huge stages and makeshift defensive structures at seven major intersections then to march to key government offices where they plan to cut water and electricity supplies.
They have promised not to storm airports or public transport.
''Bring your clothes and food with you, because we will fight for months until we achieve victory,'' protest leader Suthep Thaugsuban earlier told supporters.
Fears of more violence escalated on Saturday after seven people were wounded when motorcycle gunmen opened fire on anti-government protesters in Bangkok while rival groups clashed in several locations outside the city.
Street clashes have killed at least eight people in the past two months.
Pro-government red shirts plan to stage counter rallies in provincial towns on Monday, adding to tensions.
The turmoil is the latest in an eight-year conflict that pits middle-class urban Thais and those from opposition strongholds in Phuket and southern provinces with mostly poorer rural government supporters.
Mr Suthep, a deputy prime minister in the former military-backed government, has refused to negotiate with government representatives, insisting Ms Yingluck must resign and a so-called non-elected ''people's council'' be set-up to discuss reforms and run the country.
He told Thailand's The Nation newspaper he wants to see a peaceful ''people's revolution'' but said he would retreat if serious violence erupts.
''If it becomes a civil war, I will give up. People's life is precious for me,'' he said.
Mr Suthep, who has been charged with treason but police have not executed a warrant for his arrest, said ''I am pretty sure today that we won't lose the fight - I just don't know how we will win.''
Ms Yingluck has called a snap election for February 2 to try to end the crisis that was prompted by a failed attempt in September to introduce an amnesty bill in parliament that would have allowed her brother Thaksin Shinawatra to return from exile without having to serve a two-year jail sentence for corruption.
Offers she has made to set-up a reform body and call another election within 12 months have been rebuffed by Mr Suthep who also refused to speak with representatives of Thaksin at the weekend.
The Democrat Party, the main opposition, is boycotting the election which the organising Election Commission has recommended should be delayed after protesters in some areas prevented candidates from registering.
The protesters accuse Ms Yingluck of being a puppet of Thaksin, a former prime minister who was ousted in a 2006 coup. They accuse the Shinawatra family of endemic corruption, which Ms Yingluck denies.