Bangkok: A Thai court has reversed death sentences for two men convicted over the execution-style murder of prominent Melbourne insolvency expert Michael Wansley in 1999.

A former chairman of the Australian Red Cross who had been awarded the Order of Australia for services to charity, Mr Wansley, 58, was shot dead by a gunman on the back of a motorcycle while employed by Deloitte Touche Tohmatsu to investigate financial malpractice at Thai sugar mills.

The death penalties for Somchok Suthiwiriwan and Sompong Buasakul have been reversed.

The case that lingered through Thai courts for 16 years raised serious questions about the country's judicial system.

Thailand's Supreme Court on Wednesday reversed the death penalty for sugar mill executives Somchok Suthiwiriwan and Sompong Buasakul, handing them life sentences.