Seven people were wounded in the incident in northern Bangkok on the eve of the election.
Mr Charupong said the public already knew that the EC and PDRC were trying to derail the election. He advised people who have been prevented from voting by the incident to file a police complaint.
The EC announced on Saturday evening that voting in Lak Si on Sunday would be cancelled. It said it would not open 158 polling units in the district as officials had failed in negotiations with protesters to obtain the ballots from the blockaded district office. A new election will be held later.
The caretaker interior minister, meanwhile, was the first to cast his vote at polling unit 25 in front of the Big C department store at the mouth of Soi Lat Phrao 15 in Chatuchak district.
He called on all eligible people to vote, arguing that it is the best way to solve the country's problems through peaceful means and according to international standards.
"Without an election, we won't get a new prime minister. Regardless of who is new prime minister and from what party, the country must undergo changes which are internationally recognised," Mr Charupong said.
Among the wounded in the Lak Si gun battle was a Daily News reporter and an American photographer, James Nachtwey.