Here is the recipe I use.
4 cups water
1/2 cup cooked brown rice
1-2 Tablespoons light vegetable oil
1-2 Tablespoons honey
1/4 teaspoon salt
1/2 teaspoon vanilla (optional)
Blend in a standard beverage blender, on high speed, for 10 minutes
Strain if needed
I always use the max honey and oil, but I'd start with the lesser amounts - you can always add more!
To my taste, safflower oil tastes best. I don't generally use corn or canola (or mixed "vegetable" oils) but any of the light flavor ones would probably taste fine. Olive oil has a distinct taste that I don't like in my rice milk. Coconut oil (pre-warmed/melted) should work for milk you intend to serve fresh and warm, but might solidify and ruin any rice milk you store in the fridge.
I usually skip the vanilla, just because we are usually out of vanilla.
And cooking brown rice.... aaaaah, what an art! It took me years to figure out how to make perfect brown rice, and I still botch it every now and then!
"Perfectly" cooked rice, and slightly over-cooked and/or over-watered mushy rice, make great rice milk.
Hot fresh rice, makes great rice milk. I think it's more than the fluffy freshness, but also I think the heat helps the oil, water, and honey emulsify. (Just a guess though!)
Recent (aka, not yet in the fridge) leftover rice, makes great rice milk.
Slightly undercooked or underwatered rice, makes clumpy rice milk.
Refridgerated leftover rice shrivles a bit, and also tends to make clumpy rice milk.
Lastly, when you are blending, you may want to put a towel over the lid before you turn it on. You can probably guess why. ;)
I hope that helps some. I love rice milk.