The "Baby Milk" scam is a money-making scheme prominent in tourist hot spots in Cambodia.
Here's what really goes down: once you've agreed to help the poor young mother, she will lead you into a nearby supermarket (conveniently of her choosing), where you generously pay a large sum - something like $50 - for a can of baby formula.
As soon as you're out of sight, she creeps back into the store - where she has a prearranged relationship with the owner - and sells it back to him.
They split the profit, and that formula goes right back on the shelf.
Pair of savvy Cambodian geniuses: 1. Clueless feel-good tourist: 0.
OLDEST TRICK IN THE BOOK
Lina Goldberg, author of Move To Cambodia: A Guide to Living and Working in the Kingdom of Wonder, told news.com.au the scam has been going on for years and is difficult to contain.
"It's hard to say no, and many well-meaning visitors have bought large cans of overpriced formula in Siem Reap's Pub St area," said Lina, who first moved to the country in 2010.
"Once they get their selfie with the hungry baby and head back to their hotel, the woman returns the milk to the store for cash, and starts the process over again.
"A single baby can be bought a dozen cans of formula a night."
Lina has spoken out about the scam on her blog, but says it's difficult to stop because it works so well on travellers who haven't done their research.
"The baby milk scam has been going on in Siem Reap for years," she said. "Those of us who live here do what we can to try and stop it, but it's so entrenched, and so many tourists fall for it, that it's been very difficult to eliminate."
While I wasn't taken in by the milk scam, I've been on the receiving end of several others in Southeast Asia - dodgy taxi metres in Vietnam that skyrocket at the click of a secret button, "porters" in Bali who carry your luggage a few metres and then demand a $10 tip, and being short-changed in currency exchange stores.
After cursing my own stupidity, I'd rationalise it by saying "Hey, that money means more to them than it does to a traveller". But scams involving children are a different story. In the case of the milk scam, there is speculation that the babies are drugged - or deliberately deprived of food and water - to make them look even worse.
While many of the babies being carted around Siem Reap do look eerily still, Lina stressed child protection organisations have found no concrete proof of drugging.
In a blog post, Cambodia-based NGO Friends International said it has looked into the allegations before going undercover in the city centre to observe how the babies were treated. They concluded there was no proof that the babies were deliberately mistreated.
However, tourists giving money to such scams allow for the continuation of a dark industry that sees children used for the wrong reasons.
"Well-meaning tourists might not think it matters if it's a scam or not," said Lina. "Money is still going to a poor Cambodian family, right?
"Unfortunately, buying baby milk perpetuates a situation where older children are kept up all night and out of school so they can beg on the street, and babies and toddlers, possibly borrowed or rented from their mothers, are kept swaddled and unable to walk."
Efforts have been made to educate clueless tourists on the scam. Child protection organisation ChildSafe has English-language posters set up prominently around town, on street poles and in toilet cubicles, which warn tourists that "this is often a scam and harmful for children".
Tourists who do want to help families are best off donating to human rights organisations like Unicef, which works directly with local NGOs to help Cambodian children.
But when it comes to street scammers, the answer is obvious - just say no.
