After the enactment of the Narcotics Law, Seventh version, B.E. 2562 on 17th February 2019, there was an implementation of the amnesty programme by the Ministry of Public Health (MoPH) between 27th February and 21th May 2019, mandating persons who had previously been using cannabis products for medical purposes to notify the Food and Drug Administration (FDA) of their possession and/or use of it. The Ministry of Public Health started opening piloted medical cannabis clinics in 12 hospitals in August 2019 and Thai traditional medicine cannabis clinics in 13 hospitals nationwide on 2nd September 2019. At the time of writing this report (June 2020), there were 255 hospitals around the country that had opened a medical cannabis clinic, including those conducting research on cannabis oil extracts, and 24 Thai traditional medicine clinics. Despite these official services, there were still many medical cannabis users who did not register for amnesty or could not legally access medical cannabis via the public health system. Furthermore, there are several medical professionals who have different levels of knowledge, opinions, and experiences concerning medical cannabis. The quality of medical cannabis products available also varies considerably. A study on the current situation of medical cannabis users, suppliers, and other stakeholders is thus needed in order to understand their needs and quantify the magnitude of problems, including the number of medical cannabis users in Thailand. This study is a sub-project under the research programme to develop policy recommendations for medical cannabis in Thailand. It specifically aimed to examine patterns and purposes of the use among medical cannabis users and their perception and opinion towards the benefits and harms of cannabis and related policies. We also estimated the size of the current medical cannabis-using population in Thailand at the time of the study between the end of 2019 to early 2020. Methods This study has two parts, a qualitative study using in-depth interviews and non-participatory observations, and a quantitative cross-sectional survey. Purposive sampling was used to recruit 36 key informants, including medical professionals working in medical cannabis clinics of the Ministry of Public Health, folk or alternative medicine doctors, underground traders, not-for-profit provider groups (for example priests, folk healers, civil society advocacy groups), and home or clandestine growers or producers. A respondent-driven sample of 485 medical cannabis users was obtained, 125 from the northern region and 120 each from the central, northeastern, and southern regions. Data collection was conducted between late September 2019 and the end of February 2020. Results Of all 485 medical cannabis users, 55.7% (95% confidence interval (CI): 49.4, 62.0) were males. The highest proportion of users was seen in the late adult age group (45-65 years). About one-third had attained a tertiary education or higher. The main occupation types were business owner (16.5%, 95% CI: 11.5, 21.5) and government officer (14.2%, 95% CI: 9.3, 19.1). The average duration of current cannabis use for medical purposes was 10.5 months (range 7 – 828 days). The three most common illnesses that the respondents used cannabis for treatment were cancers (including cancers of the breast, prostate gland, lymph nodes, liver, lung, intestine, ovary, ureter, and bladder) or non-malignant tumors (23.3%, 95% CI: 16.1, 30.4); neuro-psychiatric symptoms or disorders, including stress, depression, anxiety, bipolar affective disorders, insomnia, stroke, epilepsy, multiple sclerosis, dementia, and Parkinson’s disease (22.8%, 95% CI: 17.5, 28.0) and musculoskeletal pains, spasms, rigidity or weakness (21.6%, 95% CI: 16.7, 26.6). Other diseases or symptoms that the respondents reported using cannabis for treatment were various, for example diabetes mellitus, hypercholesterolemia, hypertension, gout, asthma, chronic lung disease, anemia, liver cirrhosis, HIV-AIDS, herpes zoster, herpes simplex, psoriasis, vitreous degeneration, cataract, and low appetite. Based on the condition groups classified by the MoPH, similar percentages of the respondents reported using cannabis for the treatment of conditions in Groups A (strong evidence of benefit from cannabis, 21.5%), B (some evidence of benefit, 20.6%) and C (insufficient evidence of benefit, 21.7%). However, the highest percentage was seen in the “other” group, which was composed of other conditions that had not been classified as an indication for medical cannabis treatment by the MoPH (36.3%). Most respondents (84.7%, 95% CI: 78.9, 90.5) used an oral form of crude oil extract (unidentified tetrahydrocannabinol or cannabidiol content) while 9.2% (95% CI: 4.1, 14.2) used raw plant ingredients (flowers, leaves, or whole plants with roots and stems) and 5% (95% CI: 2.2, 7.8) used topical skin products, for example: massage oil, cream, spray, and soap. The majority used it 6-7 days per week or many times a day every day (68.8%, 95% CI: 61.4, 76.2). Most (72.6%, 95% CI: 64.9, 80.2) reported using the same amount of the product continuously since the beginning of their use for medical purposes and most (79.1%, 95% CI: 69.3, 89.0) felt that their conditions got better after use. The main source of medical cannabis products was illegal suppliers (74.0%, 95% CI: 63.7, 84.3), which included underground traders (54.5%, 95% CI: 40.8, 68.3), not-for-profit provider groups such as priests, folk healers, and civil society advocacy groups (5.2%, 95% CI: 0.5, 10.9), friends and relatives (12.2%, 95% CI: 6.2, 18.3) and home or clandestine growers or producers (2.9%, 95% CI: 0.6, 5.3). Among the legal sources (26%), the most common suppliers were modern (0.4%, 95% CI: -0.1, 1) and Thai traditional medicine doctors in medical cannabis clinics of MoPH hospitals (7.2%, 95% CI: -3.2, 17.7), medical doctors who provided care in their private clinics (12.8%, 95% CI: -0.3, 25.8), and folk doctors who were licensed for folk medical cannabis treatment (4.6%, 95% CI: 0, 9.2). Almost all respondents in the south and all in the central region reported obtaining medical cannabis from illegal sources, of which most were underground traders who were contacted via the internet or social media (of all sources: 77.8%, 95% CI: 33.5, 122.2 in the central region and 80.4%, 95% CI: 70.6, 90.2 in the southern region). Most participants (94-96%) agreed or strongly agreed with the policies regarding permission to use, sell, or home grow cannabis for medical purposes. However, 60-65% agreed or strongly agreed with the policies regarding sales and home-growing cannabis for recreational purposes. Moreover, most preferred the legal control of cannabis to be at the same level as alcohol 75.0%, 95% CI: 69.1, 81) or tobacco (75.8%, 95% CI: 69.9, 81.7), whereas 21.6% (95% CI: 15.9, 27.2) expressed the view that cannabis should remain as a substance of abuse under the narcotics control law, which should be controlled at the same level as other hard drugs such as methamphetamine and heroin. Using the number of people who were successfully granted amnesty, and received treatment from medical cannabis clinics operated by the MoPH at the same time of data collection as benchmarks, the number of medical cannabis users in Thailand in 2019-2020 was estimated to be 560,031 (95% CI: 438,774 - 677,637) and 606,153 (95% CI: 415,095 - 814,210), respectively, with an estimated prevalence of 10.93 and 11.83 per 1000 population. Our qualitative study revealed that most used cannabis based on their personal beliefs for conditions not recommended by the MoPH. Most believed that cannabis could treat any disease and did not cause any adverse effects. Most obtained medical cannabis products from illegal suppliers as they had accessed these sources before legal sources became available and they also trusted their suppliers. Furthermore, it was difficult to access the legal sources as their illnesses were not indicated as conditions for cannabis use by the MoPH. Most users agreed with the policy of legalizing cannabis for medical purposes but not for recreational purposes. Users and suppliers were mostly anonymous and contacted each other via social media. Some respondents mentioned that medical cannabis products that were sold using raw materials which are contaminated with a wide variety of toxic substances, for example insecticides or fertilizers and there have been several illegal cannabis plantations or clandestine home-growing sites. Most producers or suppliers of medical cannabis are businessmen or politicians with high influences in the areas. Additionally, the cannabis products which are sold underground are for commercial purposes rather than philanthropic or pure medical purposes. However, the starting point of medical cannabis services was often because the providers had used it for treating their own illnesses and found it worked well. In conclusion, our study reflects the experiences of medical cannabis users during the first year after the major regulatory transition in Thailand. Most users obtained cannabis from illicit suppliers and used it for various indications that were not supported by scientific evidence but appeared positive towards the results of use. Given that many people have already been using illicit medical cannabis products for a variety of conditions, there is an urgent need to facilitate access to legal and high-quality supplies, revise prescription indications with updated scientific evidence to ease physicians reluctance to prescribe medical cannabis, and provide effective mechanisms for public communication. These findings and recommendations highlight ongoing policy challenges for Thailand.