Crossing over illegally, the families risk arrest and detainment, the Phnom Penh Post reported Tuesday.
"There are many cases of children's legs being broken," one woman told the Post. "This makes them more pitiful, so they can beg a lot."
She said the the children are injected with medicine before their legs are broken.
At Thailand's Rong Kluea market, Vong Srey Leap, 30, said she has been begging across the border for more than 10 years.
"I cross over at the illegal border, walk to the market and beg with my daughter," Leap said.
Research done last year by NGO Friends found that most Cambodian child beggars in Thailand are there with family members.
The researcher found there is rarely any element of coercion surrounding the begging.