3-Moh policy launched in 2020 aims that each family has three doctors at the community, health center (or Health Promoting Hospital) and hospitals (a district hospital and a provincial hospital/regional hospital). The three-doctor policy recognize three doctors at three levels. The first doctor or Moh#1 is a village health volunteer who provide health services at community level. The second doctor or Moh#2 is health workers of a health center or a sub-district health promoting hospital providing health services at Tumbon or sub-district level. The third doctor or Moh#3 is a family medicine at district or provincial hospital. working at district level. Furthermore, 3-Moh policy aims to strengthen primary care development in Thailand. This study aims to explore lesson-learned and implementation process of 3-Moh policy in 4 target provinces namely Kamphaeng Phet, Roi Et, Saraburi and Trung. These provinces have had outstanding primary care development and they target a full-area implementation of 3-Moh policy. Mixed method was employed to capture all information. To assess an understanding and satisfaction on this policy, a total of 644 self-administered questionnaires were completed by 597 respondents who are Moh#1 and47 respondents who are Moh#2 & 3. In-depth interview was conducted among 30 administrators at provincial, district and sub-district level, and 24 healthcare providers. The study demonstrated that 3-Moh policy notably fostered an achievement of Primary Care Act B.E. 2562. In term of quantity, these 4 provinces achieve the target on registration of health and care providers to population. However, the implementation of this policy is still far from achieving its goal in term of quality which consist of “recognition, familiarity, accessibility and trustworthy”. There are rooms for improvement to achieve the goals of this policy. Key enabling factors for success are an integration of primary care-related policies among departments at ministerial level, an establishment of primary care division at provincial health office for integrated implementation and systematical monitoring and evaluation and an increase number of family doctors which is considered as a bottleneck of this policy. In addition, key challenge in the future is decentralization of health centers to local governments which is considered to affect a relationship and implementing of this policy.