The National Election Committee will soon print more than 20,000 ballots for the February 25 Senate election.
Senators are elected by votes cast by members of the National Assembly and commune councillors, totalling 11,695 voters.
Four political parties have registered to contest the election, including the ruling CPP, the Cambodia Youth Party, the Khmer National United Party and the royalist Funcinpec party.
There will be 33 polling stations around the country.
The NEC earlier this week announced the results of the draw to determine the order in which political parties are listed on the ballots for the non-universal election.
The ruling CPP drew the number one spot.
The CPP will be followed by the Cambodian Youth Party, with the Khmer National United Party in third, and fourth place going to the royalist Funcinpec party.
Sorm Sorida, deputy secretary-general of the NEC, said the committee will soon issue a public tender to find a company to print the ballots.
He said 25,950 ballots will be printed by the end of January at a cost of about $18,000.
“The extra ballots being printed will be stored in case there are issues with the others,” he said. “For example, for a polling station in Phnom Penh that has 452 voters, we will prepare 550 ballots.”
Yoeung Sotheara, monitoring officer at election watchdog Comfrel, said the fact that extra ballots are again being printed may cause public confusion.
“The NEC should give a better explanation on this issues,” Mr Sotheara said, noting that excess ballots printed in the 2013 national election and June 2017 commune elections led to rumours of rigged polls.
“However, we don’t want to say much because the ruling CPP has a lot of voters at the Senate elections,” he added.
NEC chairman Sik Bunhok has instructed provincial election committees to secure public order to guarantee an impartial and fair electoral process.
“Chiefs of provincial election committees have a duty to have a meeting once a week with relevant stakeholders,” Mr Bunhok said.
There are 62 Senate seats to be filled, 58 elected by commune councillors, two appointed by the King and two by the National Assembly.
Of the nearly 12,000 commune councillors who can vote, more than 5,000 former opposition CNRP commune seats were recently reallocated by the NEC and the majority, 4,558, went to the ruling CPP following the opposition dissolution by the Supreme Court.