Gambling is big business in Southeast Asia. How big? Citi places the gaming revenue in casino mecca Macau at $30 billion this year. With the addition of a casino by Las Vegas Sands (NYSE: LVS) in Singapore, that market is heating up, too. Macau absolutely dwarfs our hometown gambler's paradise in Las Vegas, which is not expected to reach $12.5 billion in revenue until 2014. And these Asian gambling epicenters have only just begun their growth.

So Merrill Lynch analyst Shaun Kelley went halfway around the world to scope out the local casino operations, starting with 72 hours in Macau and two days in Singapore. Send Ed Helms and Zach Galifianakis on a trip like that, and they'd come home with another massive Hangover, possibly missing a finger. But Kelley stayed on task and emerged with some solid observations instead.

Gambling traffic is high in both Singapore and Macau, no matter what time of year or day of the week you check in. In particular, the Marina Bay Sands resort in Singapore, under the aegis of Las Vegas Sands, hustles and bustles more than last year.

Then again, the Cotai Strip in Macau plunks down new casino resorts as fast as the government approves the permits. Here, the name to watch is Wynn Resorts (Nasdaq: WYNN) and its stellar management team.

In the near-term perspective, Singapore plans more infrastructure upgrades around the resorts than Macau does, sowing the seeds of potential growth over the next five or 10 years.

Good work, Mr. Kelley. The Hangover guys must be jealous of your iron-willed self-control.

Smaller players Melco Crown Entertainment (Nasdaq: MPEL) and MGM Resorts International (NYSE: MGM) hardly rate a mention in Kelley's report. That standoffish sentiment reinforces fellow Fool Travis Hoium's refreshed stance on Melco Crown and long-held skepticism of MGM.

On the other hand, our CAPS community clearly loves Melco above all others, giving it at least a two-star advantage over every other major casino operator. A 96% approval rating is hard to beat.

Burgeoning middle classes and booming tourist businesses across the region make these Asian gambling hotbeds natural sites for further investments -- both from resort builders and us common investors. There is a ridiculous amount of growth left to unlock here.

Interested in reading more about the gambling industry? Add some of the highest rollers to My Watchlist, which will find all of our Foolish analysis on these stocks: