Deputy army spokesman Col Winthai Suwaree would not say how many troops were being sent to the clash area, only that more would be manning the site.
Six people were wounded when gunfire broke out between pro- and anti-government protesters who had taken up positions 500 metres apart near the Lak Si district office.
Voting in the district has been cancelled in any case as ballots could not be obtained from the protester-besieged district office.
Troops from the 11th Infantry Regiment are now in place amid worries about more clashes overnight as the election draws near, said Col Winthai.
The army has deployed about 5,000 soldiers from Army Region 1 to help the Centre for Maintaining Peace and Order to ensure safety on the polling day.
Army chief Gen Prayuth Chan-ocha has ordered soldiers from the 2nd Infantry Division of the King's Guard based in Prachin Buri to safeguard Bung Thonglang and Bung Kum districts in Bangkok.
Caretaker Prime Minister Yingluck Shinawatra will cast her vote at the Khlong Lamchiek School polling station in Bung Kum.