Yahoo Southeast Asia appears to have developed a rather successful formula for mixing old-style journalism with new media. ComScore ranks the portal as number one for news in four of five Southeast Asian markets.

The key to this success has been reach and diversity of content, according to the site’s managing editor, Alan Soon. I caught up with Alan at the WPP Stream conference in Thailand.

For reach, Yahoo “introduces the human element” by engaging prominent bloggers in each market. These bloggers, in turn, pull in second-tier bloggers. The result is a growing and closely-knit community of influencers.

Rather than build niche markets, however, Yahoo aims to make content as diverse as possible. Instead of just news headlines of the day, for example, Yahoo Southeast Asia follows the lead of the Huffington Post in writing about a wide range of topics.

Yahoo’s importance as a portal has had no small effect on its success as a news site, but it is still surprising that traditional media have not been able to dislodge Yahoo as the leading news site.

Any theories why?