It really depends, and it's not as simple as you imply. US rice for example has more arsenic than any other rice in the world because US soil has more arsenic in it and rice is an arsenic soaking crop. So, if you eat too much rice, you really should avoid US based rice, it contains unhealthy amount of arsenic. It seems like Thailand based rice has the least amount of arsenic in it but I think we need more comprehensive research on this.

Sources

[1] https://www.consumerreports.org/cro/magazine/2015/01/how-muc...

[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1892142/

[3] https://www.bangkokpost.com/business/330866/thai-rice-has-lo...