And last week he was back, visiting the Big Mango from the Big Apple, to show creative types here how it’s done.

Pairoj earned fame in America with his long scroll paintings, done right there on the mean streets, of homeless people, many of them disabled and all of them disadvantaged in some way, yet not a pessimist in the bunch. They’d found their ways to cope. His 2014 exhibition at New York’s New Museum, “Positive Scroll”, was a meaningful success.

“My artwork can’t change the world, but I hope, by example, to uncover the positive side within individuals through the mechanisms of art and unwavering positive engagement,” he said at the time.

Pairoj obtained a bachelor’s in fine art from Silpakorn University in 2007 and four years later moved to New York and joined a group called the Thai Artist Alliance. He did a residency there in 2013 before enrolling at the Academy of Art University in San Francisco in pursuit of a master’s degree.

Now 33, he was back in Bangkok last Sunday for “Art Changes the World”, a project in which he and others worked their magic on the skywalk in front of the Bangkok Art and Culture Centre. He led a new artist collective called Thai Activist in painting portraits of homeless people. Their work quickly found buyers and the money raised was given to the SOS Children’s Village, which provides homes for youngsters who don’t have one.

A lot of the kids were on hand and passers-by paused to gawk as Pairoj and the others rendered marvellous pictures in a few skilful strokes. It took him just minutes to produce an endearing portrait of an elderly man. Nearby, Naphat Kositpipat, whose father is the celebrated artist Chalermchai, seemed able to mimic his technique effortlessly. Silpakorn art students wielded brushes as well, showing admirable dedication.

“I’m so glad to see many people come to support our project,” Pairoj said. “Thank you, brothers and sisters, for helping us reach our goal of helping the children. I’d always hoped to host an event like this and finally my dream’s come true. This powerful project will inspire other artists to help society too.”

Counting five paintings Pairoj had finished previously, in all there were 10 artworks put up for auction. Established artist Somsak Raksuwan, another Silpakorn alumnus, brought the gavel down on a handsome Bt505,000.

“I’d like to see people in society helping each other move,” Pairoj said. “All you have to do is donate a few baht or some food to needy people, or just spend a little free time talking to them, and they’ll be happy – and our society will be happier too.”

Naphat gave Pairoj full credit for prodding others to do something positive. “People might not believe that art can change the world, but it can reflect society’s ills,” he said. “People have cars and enough money to eat, but unprivileged people have nothing. Phi Pok [Pairoj] is different from most Thai artists because his determination to raise social issues comes from Western culture. Today, though, he’s inspired us to care more about what needs to be done.”