Tourism is a complex system serving human leisure needs. This study investigates the interrelationships of tourists, energy, environment, resource efficiency, and sustainable consumption and production that drive sustainable tourism policy in Thailand. The number of tourists arriving annually in Thailand has been increasing since the 1970s and in the 2010s this rate reached an average increase of 9.4 percent per year; however, if this trend continues, Thailand’s carrying capacity will be exceeded and the tourism industry may severely suffer.Therefore, the purpose of this study is to explore alternative courses to this current environmentally unfriendly trend. Systems thinking and system dynamics were employed to gain insights into the interconnected structure of tourists, the environment, and sustainable consumption and production. The business as usual approach to the continuing growth of tourist arrivals is resulting in severe environmental damage from the influx. However, a green approach entailing progressive adaptation through adopting of sustainable consumption and production will necessitate that the number of tourists growing at an acceptable rate: a rate that would allow the affected environment and tourist attractions to recover. This scenario would avoid the dangers of over-tourism and potential long-term impacts that may have, thus leading to a promising future for Thailand. The promotion of a high growth rate of number of tourists arriving Thailand was studied as a second scenario, and it found that number of tourists rose far beyond the business as usual model and, even though environmental impacts from tourism were significantly reduced, the continued high growth rate in the number of tourists would lead to environmental degradation from which recovery from would be a challenge. This latter scenario may be attractive to the tourism industry in terms of short- term profits; however, permanent damage will result. The study shows that becoming green is no longer an option: it has become a must for Thailand as it has become for many countries. Tourists numbers has been a major driver leading toward a potential undesirable future. However, an eco-friendly mindset of both consumers and service providers needs to be achieved as soon as possible to secure sustainability. Certification programs promoting sustainable consumption and production need to be widely recognized and quickly implemented in Thailand and worldwide. Effective communication will also play a crucial role in raising sustainability awareness and implementation at all levels.