The retired field marshal, riding a wave of popularity after he ousted Islamist president Mohamed Morsi last year, is widely expected to win the election that takes place in Egypt on May 26-27.
In the ballots already cast abroad, Sisi won the backing of 296,628 expats in 124 countries during voting on May 15-19, electoral committee chief Abdel Aziz Salman told a news conference.
Only 17,207 votes of the total 318,033 cast went to Sisi's sole rival, leftist leader and longtime opposition figure Hamdeen Sabbahi.
On Monday, the electoral committee said the turnout was higher than in the 2012 election won by Morsi.
Elections are open to any Egyptian citizen present abroad, on the condition they are registered and have identity cards or valid passports.
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Sisi supporters see in him a tough leader capable of restoring security and reviving an economy badly hit by three years of turmoil after the 2011 uprising that toppled strongman Hosni Mubarak.
But his opponents say that should he win the election, Egypt would see a return to autocratic rule.
A state crackdown targeting Morsi supporters has left at least 1,400 people dead and seen more than 15,000 jailed.
Hundreds have been sentenced to death after speedy trials.
Dozens of youth activists have also been jailed for violating a law banning all but police-sanctioned protests.