At present, the Royal Thai Government attempts to downsize civil servant posts amongst health personnel. This approach affects not only administrative staff, but also core health professionals including doctors, dentists, pharmacists, and nurses. This study aimed to explore the current situation and new employment modalities of health personnel and the impacts on retention and budget in the next 15 years. Cross-sectional mixed-method design was used. Data collection techniques comprised document reviews, in-depth individual interviews with policy makers and health personnel users, and group interviews with health personnel. Self-administered questionnaire survey on health personnel was also performed. Thematic analysis was used in qualitative data. Descriptive and inferential statistics were used in quantitative data. For qualitative findings, policy makers and health personnel users opined that hiring health personnel in civil servant posts usually faced bureaucratic hurdle, which at times undermined the flexibility in assigning health personnel in a position that matched their expertise. However the civil servant posts should continue to exist in certain functions, for instance, executive and financial functions. From the viewpoints of health personnel, being hired in civil servant post contributed to longer retention in the public sector due to work security and attractive benefits, especially medical benefits for family members. All interviewees agreed that there should not be too many employment patterns. If the civil servant employment were to be terminated, the replaced employments should have increased start-up salary and fringe benefits not inferior to the current civil servant benefits. This is consistent with the quantitative findings, which demonstrated that civil servant employment would cause longer retention years in the public sector despite large budget burden incurred (approximately 21,632 million baht in the next 15 years). Nurses showed longest retention years than other professionals. Comparing with other employment modalities apart from civil servant employment, hiring health personnel in the fashion similar to university staff with fringe benefits not inferior to civil servants, were likely to see longest retention years despite a relatively large budget burden (the budget size in the next 15 years equating 15,208 million baht, about one quarter of the budget used in civil servant employment, while the remaining health personnel in the next 15 years would be half of the remaining health personnel in civil servant employment). In summary, downsizing the number of new civil servant posts tended to substantially decrease budget impact but there was a trade-off in losing health personnel from the public sector. Regarding policy implications, the downsizing policy of civil servants should not be hastily implemented. Lifting the remuneration and fringe benefit of new employment modalities to the level that is on par to those of civil servants is recommended. In addition, there should be an amendment in public employment laws or regulations to create a leeway for health facilities in hiring health personnel in the way that matches their local context.