When diaper maker DSG International (Thailand) wants to know what its customers are thinking, it often turns to Lazada, an e-commerce firm majority-owned by Alibaba Group Holding.
"From (their) data, we know mothers sometimes browse at night, so we can offer flash sales when we know customers are browsing," says Ambrose Chan, the Thai company's CEO.
South-east Asia is the world's fastest-growing internet market, home to 600 million consumers from Vietnam to Indonesia via Singapore, many of them tech- and social media-savvy. They are rapidly spending more time and money online. A Nielsen study in 2015 estimated South-east Asia's middle-class will hit 400 million by 2020, doubling from 2012.
Gross merchandise value of ecommerce in South-east Asia will balloon to US$65.5 billion by 2021, from US$14.3 billion last year, predicts consultancy Frost & Sullivan.
Research firm Euromonitor forecasts internet retailing in Indonesia, for example, will more than double to US$6.2 billion by 2021, and Thailand will increase 85 per cent to US$2.8 billion.
Consumer goods firms, such as Unilever and Japanese cosmetics firm Shiseido, say the e-commerce boom allows them to push deeper into markets that can otherwise be difficult to understand and tough to penetrate due to poor retail networks and infrastructure.
"Data from Lazada has been used to position certain products where consumer preferences are different. For example, Thai customers like to buy diapers in special cartons, while Malaysians prefer multiple packs," says Mr Chan.
To reach more customers and get a better handle on their online behaviour, consumer goods companies are forging partnerships with e-commerce firms like Lazada and fashion website Zalora.
A customer who clicked on a 50 millilitre product may instead buy a smaller 30 ml product, said Pranay Mehra, vice president, digital and e-commerce at Shiseido Asia Pacific, noting that data and online selling experience can help firms bundle offers, decide on packaging and distribution, and influence where to set up a physical presence.
"This data is very powerful and very insightful, if used properly," Mr Mehra added.
Unilever, whose products range from Hellmann's mayonnaise to Dove soap, said it is seeing more demand from rural consumers in developing markets like Indonesia and Vietnam.
"With all our e-commerce partners, we're using data to help us find innovative solutions to unlock key barriers of high cost delivery and poor credit card penetration in remote areas," said Anusha Babbar, e-commerce director at Unilever South-east Asia and Australasia.
The conglomerate, which works with the likes of Singapore online grocer RedMart, Indonesia's Blibli and Vietnam's Tiki, said it introduced its St Ives skincare brand on Lazada after seeing a trend towards natural products and shopper search data.
"Traditional retailers will struggle to see customer behaviour," said Lazada Thailand's CEO, Alessandro Piscini. "We can tell if a customer is pregnant from their search behaviour."
Lazada, he said, plans to use data science to help its merchants customise offers for specific customer groups based on age, gender and other preferences.
Zalora, which sells clothing and accessories online in markets including Singapore, Malaysia and Indonesia, said it was working on ad-hoc projects with some brands to help them understand their customers based on data.
Lazada and Zalora are among the few e-commerce platforms that operate in multiple South-east Asian countries. But the region is becoming a new battleground as Amazon and JD.com make beachheads in Singapore and Thailand.
Lazada Thailand will focus on partnering with fast-moving consumer goods companies to maintain its lead, Mr Piscini said, and is expanding its logistics footprint across a region that has poor roads, clogged cities and thousands of often remote islands.
To be sure, online still contributes a tiny portion to consumer goods companies' sales, but some local firms are going beyond partnerships and investing in their own e-commerce capabilities.
Thailand's top consumer goods manufacturer Saha Group has seen online sales of some of its brands rise tenfold since it began a partnership with Lazada in June, but online still represents just 1-2 per cent of total sales.
Saha is using e-commerce data to customize offerings.
"We now make real-time offerings to customers. Before, promotions would be seasonal," chairman Boonsithi Chokwatana told Reuters.
The company, whose products include instant noodles, toothpaste and laundry detergent, is investing 2 billion baht (S$81.94 million) in logistics to support its e-commerce ambitions, including a 21-storey warehouse and a big data team, he said.