He was promoted as a Judge of the High Court of Kerala in 1985 and served as the Acting Chief Justice in 1995.

[2] During his practice as an advocate, he led an Indian delegation to attend the World Conference on Peace held at Texas, United States in 1976.

Justice Thomas presided over the Supreme Court bench that confirmed the death sentence in the Rajiv Gandhi assassination case.

[10] Though Justice Thomas wrote a dissenting note on the report of the Empowered Committee regarding the maintenance of the water level at Mullaperiyar Dam, his concurrence with the report stating that the dam was safe raised criticism in his home state of Kerala.

"[13] Another matter of public interest was his letter to the Chief Justice of India on allegations raised by Senior Advocate Dushyant Dave regarding the disposal of a 12-year-old land allotment case by a two-judge bench headed by Justice C. K. Prasad, which was actually listed before another three Judge Bench.