This is one of the great combinations. Must try steaming the rice - I've never made it that way. I usually partially cook the rice and then finish cooking in coconut milk. Sweet glutinous rice; jasmine works in pinch too.
Talking of pinches, here's a quick 'cheater' version I've made to moderate success (as in it is not the preferred method, but works). Useful for small quantities or when you have some leftover coconut milk from other things.
Mix rinsed/washed rice + coconut milk + sugar in glass bowl, microwave till done
(I generally put in liquid till it is slightly higher that the rice in the bowl, stop and stir (and add more liquid if it is getting too dry)
A long time ago I saw a you tube video with some thai ladies doing this microwave method*
Some sesame seeds with the thick coconut fat (you can skim this and reserve from the top of the opened unshaken can) with the mango works well too.
*edited to add
May have been this onehttp://www.youtube.com/watch?v=AxmNsQ_T0oc