What have I started lol.

Just because it is not as solid as a dough I would say a bit more than the normal amount. the usual ratio is 1-2% by weight of flour. I would suggest 3% so for 500g of rice you would put 15g of dry yeast.

Don't forget to add a bit of sugar otherwise it will rise very very slowly. I would add around 5% sugar by dry rice weight, but if you want less you could get away with it but it will take longer to rise.

P.s

Adding more yeast and/or more sugar will usually produce even nicer results, the only issue is that the more yeast you add the more yeast flavor you get, but personally I associate it with good bread so I love adding lots of yeast and I go for like 5%.