The election, due to take place at home on May 26, seems set to confirm incumbent Bashar al-Assad's stay in power, reports dpa news agency.
Syrians in Bahrain, Kuwait, Oman, Iraq, Egypt, the United Arab Emirates, and other countries, began casting ballots in Syrian embassies early Thursday, Syria's state news agency SANA reported.
In Lebanon, buses loaded with Syrians carrying pictures of al-Assad and waving the Syrian flag were seen heading towards the Syrian embassy on the outskirts of the capital Beirut for the one-day vote.
Earlier this month, Syria's Supreme Constitutional Court approved three candidates, including al-Assad, to run in the election.
His two competitors are Mahmoud Muri and Abdullah Saloum Abdullah.
Muri, a lawyer and a member of the Syria-based opposition, is campaigning under the banner "Together", with a prominent slogan speaking about the need to "release all political detainees".
For Abdullah, who was also a member of the Syrian parliament and a former state minister, his campaign features slogans about investments.
Al-Assad, who has ruled Syria since 2000, is expected to win a fourth seven-year term in an election derided as stage-managed.
His father, Hazfez, governed Syria from 1971 to 2000.
Neither has allowed much dissent, and both have been accused of autocracy.
In 2014, al-Assad was re-elected for a third term after winning by a landslide in Syria's first multi-candidate election.
Syria's crisis started with peaceful pro-democracy protests in March 2011.
It soon evolved into a full-blown conflict, drawing in foreign fighters and powers.