In the past few decades, the fast-growing life expectancy has raised concern over retirement issues worldwide, including in Thailand. While insufficient preparation for retirement has been known to link with negative impacts on both physical and mental health of retirees, there is still little research done on retirement preparation and planning among the Thai older person. Thus, the present study aims to determine the level of retirement preparation among formal workers at near retirement age in a public sector. This study was conducted in May-June 2021 via a 45-minute self-administered questionnaire with 226 participants aged 55-59 years old; participants were selected using systematic random sampling. A self-administered questionnaire was distributed to assess the information of sociodemographic characteristics, health status and retirement preparation. All data were analyzed by descriptive statistics such as frequency, percentage, mean and standard deviation. First, the results showed that the formal workers near retirement age in a public sector are divided into 40.3 percent female and 59.7 percent male. Most participants had a senior high school education and a couple's marital status. Many of them lived with the children, in their own accommodation together with 3-4 family members. The monthly income of participants is between 15,001 to 25,000 baht, and more than 90.3 percent of them received employee welfare benefits. Overall, participants were not preparing for retirement very well. Less than half (47.3 percent) having the preparation for retirement at a moderate level. Although 23.5 percent of participants reported that they have a high level, more than a quarter (29.2 percent) fall far short of retirement preparation. Second, quality of life and perceptions of job satisfaction were found to have a major influence on the level of retirement preparation among formal workers in near retirement age. The result of this study was expected to be useful for public sector to review and planning of retirement preparation behavior for formal workers before retirement.