Concrete barricades will spring up at key sites and mechanical metal barriers that rise from the ground at the touch of a button are likely to appear on some roads.
The police deployment for the hotly anticipated meeting is expected to be the biggest since 2006 when some 23,000 officers were mobilised for an IMF-World Bank meeting in the city-state.
Singaporeans are used to, and largely accept, tough security measures and the sight of uniformed officers patrolling the metro and armed soldiers at airports is normal.
The government has long hammered into its citizens that heavy security is necessary as the wealthy financial hub is a prime target for a terror attack.
But the extreme measures are likely to be rare even by Singaporean standards, and could disrupt the largely orderly daily life of the city's 5.6 million residents.
Music teacher Janice Tan, 28, said the security arrangements were "terribly inconvenient", particularly due to expected road closures downtown. "I care about world peace but I would prefer if they took their meeting elsewhere," she told AFP.
The decision to ban flares, banners and loudhailers at some summit venues is perhaps driven by concerns that even in a city where protests are rare and require a police permit, some may still be tempted to come out onto the streets.
Sites covered by these restrictions include Sentosa, the resort island where the leaders will meet Tuesday, and a leafy diplomatic district that takes in the Shangri-La hotel where Trump is expected to stay.
Authorities have also restricted the use of airspace, apparently to allow Kim, Trump and their entourages to get in and out of the city-state smoothly.
But that could spell problems for travellers using Singapore's Changi Airport -- one of the world's busiest international hubs -- with aviation authorities warning of delays.
There have already been signs that authorities are nervous ahead of the meeting.
An Australian former terror suspect, who was refused entry into Singapore this week and deported home, said he believed it was because of the looming summit.
A Kim Jong Un lookalike -- who said he had been to Singapore before without any problems -- was grilled by immigration officials for two hours when he arrived Friday and warned not to visit sites linked to the meeting.
Some of the heaviest security will be around Sentosa, which observers believe was picked because it is relatively far from population centres, and the island's Capella Hotel where the leaders will hold their historic talks.
An AFP photographer said hotel staff were seen turning away those without business in the area, while plainclothes security officials -- both American and Singaporean -- were spotted around a bar overlooking the Singapore Strait. While the security may be extreme, analysts think it is needed given the unprecedented nature of the summit.
"By and large Singaporeans are used to seeing men in uniform," Graham Ong-Webb, a research fellow at the S. Rajaratnam School of International Studies, told AFP.
"This time round, they might balk slightly at the number of security assets on the ground -- but it is necessary.
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