Migrant workers should be protected by labor laws of the host countries and must not be included in TISA or any free trade agreement. They are employees, not independent service-suppliers.
Mode 4 provisions under the General Agreement on Trade in Services (GATS), under the services chapters of free trade agreements, including the proposed Trade in Services Agreement (TISA), typically involve the movement of natural persons such as investors, intra-corporate transferees (managers, specialists, technical persons) and highly technical personnel such as those with expertise law, accounting, taxation, management consulting, engineering, computer, advertising, research and development services, translation services, higher education, architecture, and research and development, and the like.
One easily infers from the above enumeration that either these natural persons are trying to look for investment opportunities, or are providing highly-specialized, time-bound services. In neither case is any of them considered an employee. Hence, those deployed under Mode 4 who provide services by way of a contract for service do not expect any protection under the labor laws of the host country, and their contracts are instead governed by default contract laws.