It is widely known that systematically developed training manuals can be used to improve knowledge and practical skills and promote positive attitude of trainees. This research thus aimed to develop a training manual to help reduce the use of pesticides by para rubber farmers in Nonkheng Sub-district, So Phisai District, Bueng Khan Province, Thailand. The research was divided in to 3 stages. The first stage investigated the scenarios in which pesticides were used of the para rubber famers while the second stage dealt with the development of a training manual for promoting the reduction of the use of pesticides and hazardous chemicals by the farmers. The final stage was the evaluation for the efficiency of the developed training manual by applying it with 48 volunteered para rubber famers for 2 days. The findings revealed that the training manual had an efficiency of index at 80.38/80.89. After training with the manual, the farmers' levels of knowledge increased tal 67.40%, while the overall post-test scores on knowledge, attitude, and practice skills in reducing the use of pesticides were found to be significantly higher (p < 0.05) than those of the pre-test. It can be concluded that the developed training manual can be effectively used to improve the knowledge, attitude, and practical skills of the trainees.