The government of Thailand aims for sustainability of palm oil production in the Northeast for bioenergy and farmers’ income. This study investigated whether producers in Northeast Thailand managed their oil palm according to good agricultural practices (GAP) and if not, what effects this has on yield. A survey was conducted amongst 108 randomly selected farmers. For 25 selected plots, management and yields were monitored twice a month for two full years. Compliance to GAP was high for weeding, harvesting, pruning and pest and disease control but not for irrigation (40%) and fertiliser application (20–40%). GAP adoption scores per households positively correlated with income from other crops, tree age and degree of training. We showed that rainfall was insufficient for good oil palm growth between October and April. In the monitored group, use of irrigation and amounts of N, P, K and Mg applied were strongly correlated. The yield was significantly greater with irrigation and fertiliser, reaching similar levels as in the South of Thailand (up to 25–30 Mg Fresh Fruit Bunches: FFB ha−1), but did not differ with soil texture. This allows us to conclude that better application of GAP, especially including a combination of irrigation and fertilisers overcame the unsuitable soil and rainfall conditions in the Northeast of Thailand. However, the costs of fertilisers compared to the price of FFB affected the profitability of FFB production, which may affect farmers’ motivation to apply GAP, especially on unsuitable soils. When the government aims for sustainable palm oil production in the Northeast it needs to invest in frequent technical support, irrigation infrastructure and affordable fertilisers. Otherwise, farmers may not apply GAP because of low returns on investments and yields will remain very modest.