The protesters have blockaded seven large intersections in the capital Bangkok and forced many ministries and other bodies, including the central bank, to close their doors.
With staff working from home or back-up facilities, the government has asked protesters to discuss ways to free up access.
But protest leader Suthep Thaugsuban said: "Groups in each protest area will not negotiate with government officials to return the various premises, so don't bother contacting us."
Meanwhile, Thailand's Election Commission has urged delaying Sunday's planned general election, warning of more bloodshed after violent clashes at the weekend.
That would drag out a crisis that risks splitting the country. The military, which has often stepped in to take control in the past, is staying out of the fray this time, despite appeals from anti-government protesters.
Somchai Srisutthiyakorn, an Election Commission member, said: "As election officials, it is our job to make sure elections are successful but we also need to make sure the country is peaceful enough to hold the election. We don't want it to be bloody."
The commission is due to meet embattled Prime Minister Yingluck Shinawatra today to discuss the date of the vote.