Singapore is for residents/citizens only and close to Malaysia with its strict approval. Taiwan is less strict but requires the same documentation as workcation for Sotfpower applicants regarding evidence of income, Taiwan requires just a final balance of 500k along with 3-6 months of bank statements.
Mesotherapy is a medical treatment for hair loss so it should come under the medical DTV option. You will need to show a 6 months plus treatment plan. One session each 4 months? ? you mean one session a month ? a session every 4 months will very likely lead to a rejection.
Tobias Schmiedeberg Vietnam is more strict now approving SP applicants. Jakarta, Laos, Cambodia are friendlier. Did you provide a budget e.g 40k Euros will cover e.g
Anonymous participant Yes it is, but unfortunately due to recent visa violations in Thailand, there is stricter approval of Chinese applicants. Other Chinese posted last month or so about this. I know some rejected in Vietnam who got approved in Indonesia. Jakarta is more "friendly".
In terms of work The DTV is for online work only and for non -Thai firms. The other DTV option is via activity such as Muay Thai, Thai cooking or Medical treatment. You apply outside of Thailand and need to stay in the country of application until approved. Some countries like Laos, an interview is compulsory, others case by case. Cost is 10k THB but can vary depending on the embassy exchange rate. Can take 10 business days to one month depending where you apply. Cambodia 4-6 weeks.
Unemployed applicants have been approved for the DTV. How long was the Muay Thai course? You can apply right away at another embassy, Jakarta, Laos are good options. Triple check your application before applying again. Did you include a cover letter detailing your long term need for the DTV via Muay Thai?
There are delays in Vietnam at the moment, Cambodia too Using an agent won't speed things up, they only do what you would yourself do. Hopefully you get your approval very soon.