Ammonia (NH3) co-firing is a promising strategy to lowering the CO2 emissions from fossil fuel combustion. Indonesia is currently pursuing green ammonia production using plentiful renewable resources like geothermal and hydropower. As the country aims to achieve net-zero emissions by 2060, incorporating green ammonia into existing thermal systems, particularly in the power and industrial sectors, provides a possible transition path. However, the potential for significant increases in NOx emissions may hinder widespread NH3 co-firing capture. This study investigates the effect of ammonia injection position on flame stability, combustion temperature, and NOx emissions in a lab-scale co-firing system using LPG and ammonia, simulating partial ammonia substitution in industrial burners. Five axial injection positions were tested to assess the influence on emission characteristics and flame performance. The results show that downstream injection of ammonia significantly reduces NOx emissions due to lower flame temperature and delayed ammonia oxidation, whereas upstream injection yields higher thermal output but increases NOx formation. The findings of this study contribute to the development of low-emission co-firing strategies, supporting the feasibility of green ammonia as a scalable, clean fuel in Indonesia's decarbonization agenda.