Hanoi's small business owners are making a killing selling merchandise linked to the visit by US President Donald Trump and North Korea's Kim Jong Un.

Truong Thanh Duc's Trump and Kim t-shirts are selling like hotcakes in Hanoi. (AAP)

T-shirt printer Truong Thanh Duc is making international headlines as the world directs its attention to this week's summit between US President Donald Trump and North Korean leader Kim Jong Un in Hanoi.

From his shop on Hang Bong street in the Old Quarter, Duc prints and sells his own designs and his shirts of Kim and Trump's faces have caused a surge of interest.

On the first day, he sold 300 at 100,000 Vietnamese dong ($A6) each. By the second day he couldn't keep up with demand.

"I'm not taking much of a mark-up but I love selling it out of love for these great men," he said.

As talks set for Wednesday and Thursday approach, Hanoi's small business owners, from barbershops to bars, are cashing in.

Le Tuan Duong, owner of the Tuan Duong Beauty Academy hair salon in Hanoi's Dong Da district, decided last week to offer haircuts in the style of Kim and Trump.

Those opting for the more popular Kim look get their hair moulded and slicked back in the style of the North Korean leader, while those preferring Trump have their hair dyed in the president's distinctive blond hue.

Proud of his country's hosting of the summit, Duong said the haircuts were a celebration of his patriotism.

"I want to advertise my love of my country to the world," he said, adding he was a fan of both men.

By day four of his promotion, he said he'd given out 200 Kim and Trump cuts, mostly the former as the natural, jet black hair of most Vietnamese people more closely resembles the North Korean leader's.

Meanwhile, an Irish chef in Hanoi is serving a cheeky menu, with Durty Donald and Kim Jong Yum burgers on sale at the Durty Bird restaurant.

Co-owner and head chef, Collin Kelly, says the burgers are also designed to capture the likeness of the leaders.

Kelly said the Durty Donald was like Trump himself - "so extravagant" - with double beef, double bacon, topped with strands of yellow chicken floss.

"To match some of the controversy that surrounds him, we've put Russian dressing on it. So a bit tongue and cheek but I think he'd see the funny side," Kelly said.

Across town on Truc Bach lake, a trendy bar serving microbrews has launched a kimchi-infused sour ale the brewers have named Kim Jong Ale.

SBS News