He was born at "De la Brooke Manor" in St. Mary's County, Maryland on March 11, 1785, the son of William Thomas and Catherine Boarman.

He was elected governor by an overwhelming majority in 1833, the last anti-Jacksonian candidate to be chosen before that party became the Whigs.

During his term occurred the removal of the government deposits which preceded the failure of the Bank of Maryland during 1834.

This incident prompted Governor Thomas to take measures for the establishment of a state militia organization.

He died there on Christmas Day 1845, and was buried in the Thomas’ family cemetery at "Deep Falls".