China may have a large amount of rice that can export to various parts of the world, but they are not the largest exporter of rice. There was also a time when Thailand used to export rice probably because they also have some nice rice varieties that people cannot help but like. You just need to taste Mango sticky rice in order to see the difference with the rice that is being offered there.
However, right now, India is considered to be the largest exporter of rice. It has already exported a million tons of rice to various parts of the world starting from the year 2015. This is likely to become even bigger in the future.