With consumer price inflation at 37 percent according to the latest central bank estimate, demand has pushed a kilogram of rat meat up to around 5,000 riel ($1.28) from 1,200 riel last year.
Spicy field rat dishes with garlic thrown in have become particularly popular at a time when beef costs 20,000 riel a kg.
Officials said rats were fleeing to higher ground from flooded areas of the lower Mekong Delta, making it easier for villagers to catch them.
"Many children are happy making some money from selling the animals to the markets, but they keep some for their family," Ly Marong, an agriculture official, said by telephone from the Koh Thom district on the border with Vietnam.
"Not only are our poor eating it, but there is also demand from Vietnamese living on the border with us."
He estimated that Cambodia supplied more than a tonne of live rats a day to Vietnam.
Rats are also eaten widely in Thailand, while a state government in eastern India this month encouraged its people to eat rats in an effort to battle soaring food prices and save grain stocks.