Although it may exist, I've never seen or even heard of rice malt and I doubt the breweries use it.
Instead, they use a very light barley Pilsner malt and a large percentage of rice (40% or more) as an adjunct. 6-row barley is generally preferred as it has more diastatic power than 2-row, as well as a higher percentage of husk material for better lautering. Rice yields very little flavor to beer, even less than corn. This makes for all those pretty much flavorless light lagers the majority of people seem to like. Think of the light and ultra light lagers Budweiser, Coors, Miller, etc. sell billions of gallons of each year. Asahi belongs to that style group, and is possibly brewed with an even higher percentage of rice (>40%).
Of course this beer needs to be brewed all-grain and requires mashing. I doubt a partial mash with extracts will give anything close to what's expected.
One could use minute rice, as it's already pre-gelatinized. When using regular rice it needs to be boiled in a lot of water for an hour or so and/or cereal mashed with a diastatic malt (e.g., 6-row barley). Some wheat malt can be added too.
Needless to say, beer that is so light and has such little flavor is actually very difficult to brew right, since even the smallest flaws stand out, potentially ruining the light lager "experience."