Thailand is a nation with a population of around 69,800,000, of which 93.20% adhere to the state religion of Buddhism. Therefore, if a person converts to Christianity, they are no longer considered fully Thai. This worldview creates a passive resistance to change and presents a constant challenge for Thai pastors and church-planters. While some research has examined Bible school training and Christian leadership in Thailand, little work has focused on in-service training for Pentecostal leaders in Northern Thailand. My research will be conducted by utilising a qualitative analysis approach. Supported by secondary literature, the methodologies will be oral interviews with local church leaders, participant-observation and a case study on Thailand Assemblies of God churches in Chiang Mai province. Through this research, I expect to discover the information and training gaps that local Thai leaders identify between their initial Bible school training and the reality of daily ministry challenges. On the basis of the data gathered, I will develop and pilot an in-service leadership development program that seeks to equip leaders with keys to growing healthy churches. I am particularly well suited to researching this issue as I have spent the last 38 years as a missionary and missionary trainer, serving in leadership training and development programs in Thailand and North Asia. I am also fluent in the Thai language.