Background: Consuming salty foods raises blood pressure because of their sodium and salt. Educating hypertension patients about sodium contributes to their diets and can decrease the future effects on their health. Objective: The objectives aimed to investigate the knowledge about the sodium content in different condiments and raw foods, consumer preferences regarding sodium-rich foods and condiments, the sodium levels in local food, and the urine of hypertensive patients at Nakhon Si Thammarat Province, Thailand. Material and methods: The total sample size consisted of 203 individuals. The data collection tool consists of two components: the questionnaire used to assess knowledge and behavior related to consuming foods containing sodium, and the salt meter and the ion-selective electrode (ISE) were the instruments applied to the determination of sodium in food and urine, respectively. Descriptive statistics including averages and percentages, and analytical statistics, namely analysis of variance (ANOVA) were employed. Results: The study revealed that the sample was mostly made up of females, married, aged over 60 years, and had finished primary education. Participants were most knowledgeable about condiments, especially fish sauce, shrimp paste, and fermented fish. Hypertensive patients have a modest level of awareness regarding sodium. The shrimp paste had the highest consumption behavior, followed by fish sauce, monosodium glutamate (MSG), and seasoning powder or soup cube at a moderate level. Sour soup with mullet fish, stir-fried luffa with eggs, and Nile tilapia fish sour soup with taro stalk are the top 3 southern local meals preferred to consume and are rich in sodium. The sodium in the food of the lowknowledge differed considerably in moderate and high knowledge (p < 0.05). In contrast with urinary sodium, in the high-knowledge group, it was considerably different in low and moderate knowledge (p < 0.05). Conclusions: Hypertension patients’ degree of knowledge has a significant role in determining their health and ability to lower blood pressure, particularly about using spices that include sodium, and their consumption habits of local foods high in sodium.