The verdict in one case being pursued by Natural Fruit is to be delivered next Wednesday, with a second case brought by Natural Fruit against Mr Hall scheduled to begin the following day.
Mr Hall's supporters say that public demonstrations will be held outside Thai embassies in Washington, London, Helsinki and The Hague on October 29.
The international union movement is throwing its weight behind calls for the pineapple processor to drop a series of cases against Mr Hall, brought after he reported on conditions for migrant workers for an NGO, Finnwatch.
As Mr Hall was the only member of the team conducting the research who resides in Thailand, Natural Fruit opted to sue him using the country's controversial criminal defamation laws and the draconian Computer Crimes Act.
The same much-criticised laws have been used by the Royal Thai Navy to sue two journalists at Phuketwan, Chutima Sidasathian and Alan Morison, and by expats with poor reputations - and in some cases past criminal convictions - to sue British investigative journalist Andrew Drummond.
Public demonstrations next week in the US and three major cities in Europe are likely to alarm Thailand's Ministry of Foreign Affairs, food exporters and the tourism industry and intensify calls for Thailand's military government to intervene to save Thailand's reputation.
The use of bad laws by private companies, by the Royal Thai Navy and by expat rogues to silence human rights defenders and investigative journalists has been widely criticised inside and outside Thailand.
The Finnwatch report, 'Cheap Has a High Price,' exposed smuggling of migrant workers along with the use of child labor, forced overtime and violence against factory workers.
The large International Transport Workers' Federation (ITF) said last month that Thailand itself is on trial over these abuses.
Mr Hall has since turned his attention to the welfare of the two Burmese charged with the murders of British tourists Hannah Witheridge and David Miller on Koh Tao on September 15.
In defending expats and Thais from Pattaya fraudsters and conmen, journalist Andrew Drummond has been forced to fight an increasing number of cases where criminal defamation is being used to silence him and exhaust his funds.
The trial of Morison and Khun Chutima resumes in July next year.
Charges brought by the Royal Thai Navy cite a 41-word paragraph from a Pulitzer prize-winning Reuters special report on the Rohingya boatpeople.
Reuters and other news organisations in Thailand that published the same paragraph have not been charged. The charges were laid before the military takeover in Thailand.
So far, the Thai government has failed to respond to a call from two UN Special Rapporteurs to have the Navy justify the case or end proceedings.
Morison and Khun Chutima face a maximum of seven years in jail. Morison's passport has been seized.
The Phuketwan news site may have to close in February when it will be impossible for Morison to renew his annual work permit.