His People's Action Party is widely expected to comfortably extend its 66-year dominance in the city-state.
But the election is being closely watched for whether the opposition can make further gains as people express unhappiness over tight government control and a high cost of living.
Wong, a US-trained economist who is also finance minister, has appealed for a resounding mandate to steer trade-reliant Singapore through economic turbulence following US President Donald Trump's tariff hikes.
The government has lowered its trade forecast and warned of a possible recession.
"This election is couched as a test of the support for the leadership of PM Lawrence Wong but it also will reflect how politics in Singapore are changing, namely an embrace of alternative voices and a younger generation seeing the PAP" under a younger leader, Southeast Asia political expert Bridget Welsh said.
Wong, 52, succeeded Lee Hsien Loong to become the city-state's fourth leader. Lee stepped down in May 2024 after two decades at the helm but remained in the cabinet as a senior minister.
His retirement as premier ended a family dynasty started by his father, Lee Kuan Yew, Singapore's first leader, who built the former colonial backwater into one of the world's richest nations during 31 years in office.
More than 1200 polling stations in schools, public housing blocks and other areas shut after 12 hours of voting on Saturday.
Polling in Singapore is compulsory, with nearly 2.76 million eligible voters.
The PAP has secured five of the 97 parliamentary seats because they were unopposed.
The Election Department said turnout was about 82 per cent three hours before voting ended.
Results are expected to be known in the early hours of Sunday.
The PAP is seen as a beacon of stability and prosperity, but its government-knows-best stance and the rising cost of living in one of the world's most expensive cities also has led to growing unhappiness, especially among younger voters.
Widening income disparity, increasingly unaffordable housing, overcrowding and restrictions on free speech have loosened the PAP's grip on power.
The PAP's share of the popular vote slipped to a near-record low of 61 per cent in 2020 elections, down from nearly 70 per cent in 2015. Although it kept 83 out of 93 parliamentary sets, the opposition gained grounds with a record 10 seats.
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