RESUMEN
Various basic occupational health services (BOHS) are provided, particularly in-plant BOHS; however, it might be necessary to start expanding BOHS. The current study focuses on BOHS model development using participatory action research (PAR) at a large-sized enterprise in northeastern Thailand. The PAR began with a situation analysis using ILO Convention C161, problem and cause analysis, the development of an action plan, observation and action, evaluation, and replanning. The research tools included interviews, focus group discussions (FGDs), and participant observations. The participants included managers, human resource staff, safety officers, and workers. Both inductive and deductive thematic analyses were undertaken. The results showed that (1) education and learning experience led to the workers detecting work-related diseases early by themselves and the implementation of medical surveillance programs; (2) the workers' occupational health needs led to return-to-work assessments and first aid room system development; (3) the employer's experience led to appropriate fit-for-work examinations and emergency preparedness; and (4) the feedback from BOHS providers led to a hospital-to-in-plant return-to-work conversion. The study concluded that the enterprise could develop fit-for-work and return-to-work assessments as per the ILO Convention C161 under the policy; however, medical surveillance and the first aid room system need to be developed through counseling at the hospital's occupational medicine clinic.