Before he started a company 15 years ago selling the world’s smelliest fruit, Eric Chan had a well-paying job writing code for satellites and robots. His family and friends were puzzled when he made the career change.

The fruit, durian, has long been a cherished part of local cultures in Southeast Asia, where it is grown in abundance. A single durian is typically the size of a rugby ball and can emit an odor so powerful that it is banned from most hotels. When Mr. Chan began his start-up in his native Malaysia, durians were cheap and often sold from the back of trucks.

Then, China acquired a taste for durian in a very big way.

Last year, the value of durian exports from Southeast Asia to China was $6.7 billion, a twelvefold increase from $550 million in 2017. China buys virtually all of the world’s exported durians, according to United Nations data. The biggest exporting country by far is Thailand; Malaysia and Vietnam are the other top sellers.

Today, businesses are expanding rapidly — one Thai company is planning an initial public offering this year — and some durian farmers have become millionaires. Mr. Chan is one of them. Seven years ago, he sold a controlling share of his company, which specializes in producing durian paste for cookies, ice cream and even pizza, for the equivalent of $4.5 million, nearly 50 times his initial investment.

“Everybody has been making good money,” Mr. Chan said of the once-poor durian farmers in Raub, a small city 90 minutes from Kuala Lumpur, the Malaysian capital. “They rebuilt their houses from wood to brick. And they can afford to send their children overseas for university.”