The government has said that text messaging will be restored after polls close at 3pm.
King Norodom Sihamoni, in a message broadcast on Friday on state-run television TVK, urged voters to cast their ballots without fear of threat or intimidation from any person or party.
"Please freely exercise your rights to vote according to your own conscience and trust in any candidate or party," he said.
The ban followed a request from the National Election Committee, So Khun said, referring to it as part of a necessary "tranquility period".
The election committee chairman, Im Suosdey, also said the committee was concerned that political parties could use mobile phones «to send messages to 20 or 30 people at a time to galvanise them to vote for their parties».
Being inundated with text messages could spoil the calm ahead of voting and on election day itself, he said.
But the Sam Rainsy party, the sole opposition party with parliamentary seats, said the ban as unlawful.
Mu Sochua, the party's secretary-general, has said that the ban curbs people's freedom to communicate as guaranteed by the constitution.
Twelve political parties are fielding 102,266 candidates in the polls, held every five years.
The first local election was held in February 2002. Previously, communes were ruled by chiefs appointed by the interior ministry.
Prime Minister Hun Sen's ruling Cambodian People's Pparty, which has maintained a firm grip on power over the past three decades, easily won the last local elections and is virtually certain to be victorious again.