Latex production of Hevea is controlled by factors related to the mechanisms of latex flow and regeneration. The mechanisms are mainly concerned with tapping systems, stimulants and climatic conditions and the results can be measured as physiological parameters in the laboratory. Since 1989, the new planting area forr rubber plantations in Thailand has shifted to the upper latitudes where the average rainfall is 1200 mm/year. The present paper reports the rresults of a combination of two experiments which employed over-exploitation (over-stimulation with the 1/2S d/2 tapping system) and over-intensive tapping to induce TPD symptoms. Latex samples from eight-year-old trees of clone RRIM 600 were collected and analyzed in the laboratory for sucrose content, thiols content, inorganic phosphorus content and DRC which are the physiological parameters which provide diagnostic information from latex. Over-stimulation treatments caused a drastic decline in sucrose content in latex 3 months after ethephon application. Thiols content of latex from stimulated trees decreased slightly compared to latex from control trees. Inorganic phosphorus increased greatly, the highest values being 25mM. The drc of latex decreased slightly after stimulant application. In the over-tapping trial, the first year result showed that high intensity tapping did not cause a decrease in sucrose content of latex but did cause a slight increase in thiols content. Inorganic phosphorus of latex from treated trees was higher than in latex from control trees, the highest value being 20mM. Over-tapping did not induce signs of TPD compared to an increased stimulant concentration however stimulated trees had a higher percentage of Dry Cut Length (DCL) than rubber trees from the high intensity and normal tapping (1/2S d/2) groups.