PurposeThis paper aims to develop indicators of happiness in learning of the Thai Open University (TOU)'s undergraduate students.Design/methodology/approachSampling for the study was comprised of two groups. Group I comprised eight lecturers who are experts in their disciplines, and six students who were purposively sampled. The focus group was used to validate the appropriateness of the indicators. In Group II, 332 students were engaged in a multistage sampling process. The responses were analyzed using descriptive statistics, coefficient correlation, exploratory factor analysis (EFA) and confirmatory factor analysis (CFA).FindingsThe indicators of happiness in learning of undergraduate students of TOU were classified in six categories. These included satisfaction with learning environment (five indicators), learning anxiety (five indicators), satisfaction with learning (five indicators), enthusiasm to learn (six indicators), self-satisfaction (six indicators) and readiness to learn (seven indicators). The six categories explained happiness in learning of undergraduate students of TOU at the 65% and fit empirical data.Practical implicationsThe TOU can use the indicators for the assessment of happiness in learning of its students as well as guidelines for the improvement of its student learning environments.Originality/valueThere have been very few studies on indicators of happiness in learning of TOU students. Most were done at the basic education level. This study disclosed the six factors affecting happiness in learning of TOU students; therefore, it should inspire and draw attention of many in the field of higher education distance learning.