During the past 10 years, there has been a considerable increase in highland maize farming in Nan. The increase in farming area causes an excessive forest encroachment and environmental problems, e.g., soil degradation, landslide, and pesticide contamination. One of the main reasons for this is the rapid expansion of maize farming area owing to the drastic increase in maize price, together with the government’s ineffective enforcement in forest conservation. Attempts made both at the national and local levels in the past to reduce highland maize farming have not shown much success. Maize farmers do not find it easy to leave their accustomed cultivation practice on highland in search of a more eco-friendly alternatives. Several reasons can be used to explain this sluggishness. For most highland farmers, once engaged in maize farming, they got locked into cycle of informal debt due to maize’s high production cost. Without sufficient and concrete incentives to induce change in farming behavior, it seems highly unlikely that the farmers would be able to reduce highland maize farming. The government policy to directly intervene or guarantee maize price, although intended to help relieve farmers’ endless problem of poverty, has indirectly fueled the maize farmers to expand their farming land and get locked into the vicious cycle of highland maize farming even deeper. Nonetheless, there are some areas that not only managed to resist the alluring market force of maize, but also found way to rehabilitate and conserve forests using local participation as the most vital mechanism. The Nam-Meed watershed has beautifully succeeded in the reforestation and reduced highland maize farming. The engagement of farmers in specifying and enforcing forest rule and regulations, coupled with appropriate role and timely supports by the officials of Nam-Meed Watershed Management Unit are believed to create profound impacts on the farmers’ attitudes toward conservation. In a rather different context, the Sop- Sai watershed has also managed to trigger a transformation from highland maize farming to reforestation. Since 2009, the area has received assistance in form of large-scale incentive scheme from “Pidthong Lungpra” foundation whose aims were to alleviate poverty problem, improving farmers’ livelihood and reduce deforestation in watershed area. This incentive mechanism has started to show significant results in changing farmers’ highland farming behavior, as they deserted maize farming to grow perennial economic trees. This research interviewed and surveyed data from 6 villages in Nan: 3 villages in Nam- Meed upper-watershed and 3 villages in Sop-Sai upper-watershed, so as to understand the fundamental mechanism and common factors which drove a sustainable natural transformation from maize farming to reforestation. The objectives of this research are to 1) demonstrate the possibility of a win-win solution in which farmers have higher incomes while forest is also restored; 2) analyze the effectiveness of various subsidy schemes; 3) explore important factors influencing farmers’ decision in reducing their highland maize farming; and 4) suggest plausible policy recommendations which lead to a reduction in highland maize farming. We found that the fundamental mechanism driving a sustainable transformation from highland maize farming to reforestation comprises 3 pillars; these are 1) adequate returns from the alternative practices; 2) a genuine love and attachment towards the forest and 3) effective enforcements of communal rules and regulations. These pillars essentially reinforce one another and are crucial factors for achieving the win-win solution in the long-run. According to surveyed data, alternative practices which can be used as a substitution for maize farming in highland can be either crop rotation in flatland, tree plantation in highland (economic forest), or reforestation in highland. With proper supports, these alternatives potentially generate higher income than maize farming in highland. In other words, farmers naturally quit growing maize in highland in search of higher income from a more forest-friendly alternative. To opt for any of the three alternatives or their mixture depends largely on the areas’ geographical and social conditions. While investigation of the natural transformation in Nam-Meed area highlighted the availability, allocation, and utilization of flatland as key driver of the change, such requirement does not always hold in the area where a rapid transformation was called for, like in Sop-Sai watershed. Subsidy schemes were used to supplement returns from new alternatives and to overcome limitations (e.g. geographical limitation) during transitional period. Using survey data from the area, we found that farmers of diverse socioeconomic backgrounds valued subsidy schemes differently. In order to successfully incentivize farmers’ behavior, the effective subsidy must take into account farmers’ socioeconomic characteristics and the area’s limitations. Our findings do not support a “one size fits all” subsidy approach. The first and foremost policy recommendation for the government is to send clear and strong signal of her commitment to solve the issue of deforestation in highland. Coherent directions of both agricultural policy and natural resource management are urgently needed. While the agricultural policy can aim to support alternatives that are contingent on ecological richness, the policy from a natural resource management standpoint cannot completely detach forests from local or indigenous people. Local community which conserves forests should be allowed not only with a balanced use of the forest, but also a communal right to regulate such use. In addition, collaborations from private sector in sending clear market signals are considered vital in supplementing government’s efforts. Price mechanism as well as maize standards are examples of channels for appropriate signals.