This paper examines how Thailand promotes education for sustainable development; it is known as the sufficiency-based school movement. The sufficiency-based schools apply the principles of His Majesty the King of Thailand’s Sufficiency Economy Philosophy (SEP) in a whole-school approach manner. SEP offers a decision making framework based on three principles - moderation, reasonableness, and prudence - along with two conditions of virtues and knowledge, while addressing balance development of environmental, social, cultural, and economic progress. SEP school movement aim to cultivate sufficiency mindset and practices in students’ daily lives by embedding SEP in the curriculum and school activities in age-appropriate ways. The movement also encourages school administrators to role model the principles, and expand to community partnerships. More than 18,699 out of approximately 40,000 schools in Thailand have been certified as sufficiency-based. 68 accredited Sufficiency Educational Learning Centres (SELCs) help mentoring applicant schools. Two phases of research were conducted. The first phase qualitative research studied the practices, success factors, and outcomes of nine SELCs. The second phase survey research studied 178 schools to evaluate the outcomes and their relationship with sufficiency-based school practices identified in the first phase. Outcomes of students in grade 6, 9, and 12 in different categories of sufficiency-based schools (the first level category, the second level ‘Best practice’ category, and SELCs) were studied. The first phase findings uncovered five key SELC practices: readiness preparation of sufficiency learning; sufficiency based curriculum; wide-ranging school activities; encouraging sufficiency habits in individuals and the community; and program expansion to other schools and communities. Furthermore, the key success factors include: faith in sufficiency principles, shared personal characters based on SEP, professional development of staff; expertise in sustainability education; a sustainability curriculum; an enabling environment, multi-stakeholder partnerships; and focusing on socio-cultural dimensions of sustainability rather than a sole focus on ‘green’ agendas. The second phase findings revealed higher averaged Ordinary National Educational Test (O-NET) scores of students from sufficiency-based schools than the averaged national standard in 2008, 2011, 2014 (excepting Grade 12 student scores in 2008). Sufficiency-based school students had a higher level of proficiency than students in other schools in five competencies (life skill, communication, logical thinking, problem solving and IT literacy) and nine desired characters (sufficient living, good citizenship, willingness to learn, integrity, diligence, discipline, healthy body and mind, local heritage pride, and national loyalty), excepting the grade 12 students in the first level sufficiency-based schools. Local communities where sufficiency-based schools were situated had a higher level of changes and satisfaction than other communities. SELCs and BP schools received very high scores in all five key practices, identified in the first phase. Other non-SEP schools received very high scores in only three practices, excepting curriculum and networking to expand results. The study found curriculum to be positively related to the O-NET scores for grade 9 and grade 12 students, and the desired character of grade 12 students. The network expansion is found related to competencies and characters of grade 9 students and community satisfaction. Finally, challenges for the future of the sufficiency movement in Thai schools are discussed.