Saudi authorities arrested Hassan Farhan al-Maliki in September 2017 and have detained him since, finally bringing charges in October 2018, according to the official website of HRW on Saturday.
"Saudi Arabia's real road to reform lies in allowing religious thinkers like al-Maliki to express themselves without fear of arrest and possible execution," said Michael Page, deputy Middle East director at Human Rights Watch.
He said al-Maliki's prosecution for peacefully expressing his religious views contradicts Saudi Crown Prince Mohammad bin Salman's claims in October 2017 that he wanted to make reforms.
Saudi Arabia has lately stepped up politically-motivated arrests, prosecution and conviction of peaceful dissident writers, human rights campaigners and independent clerics.
Saudi officials have also intensified security measures in the Shiite-populated Eastern Province.