Due to limited resources, private pre-school children have been excluded from public caries-prevention programmes in Thailand. A prepaid oral care plan (POCP) for private pre-school children was proposed to alleviate the caries and financing problems. Objective: To explore whether the market for POCP exists, a payment card (PC) questionnaire and a Willingness to Pay (WTP) measure, was applied to elicit parents' WTP. Methods: PC questionnaires were randomly assigned to 330 parents of private pre-school children in Sa Kaeo province, Thailand. Following the WTP question, respondents were asked to identify their degree of certainty about their WTP answers. 166 respondents returned the questionnaires. An effective calibration of hypothetical and real behaviour was then applied to calibrate the hypothetical WTP data. Results: The calibrated hypothetical WTP estimated that approximately 39.2% of the parents were willing to pay the unit cost of the POCP. The estimate has shown that the market for the POCP does exist. Moreover, the results of patient satisfaction assessment, obtained from the pilot POCP initiated and run for six months, have shown that an overall satisfaction score was 8.18 out of 10 and that 84.2% of those participating in the assessment decided to continue with the POCP after the pilot programme was completed. Conclusions: Given the initial stage of the POCP, approximately 39.2% of the parents interested in the POCP has shown a good possibility of the programme to be established. A high level of patient satisfaction and a high proportion of policy renewal have also shown a good sign of faith in the scheme. Thus, the POCP could be an effective method for extending preventive oral services to more pre-school children. The next step is to establish effective social marketing using schoolteachers as a key strategy. This study was supported by the Office of Educational Affairs, Thailand.