Can I freelance for Thai clients on a DTV visa?

No. The Destination Thailand Visa (DTV) is designed for people who work remotely for overseas employers or foreign clients. It does not allow you to work for Thai companies or provide freelance services to clients based in Thailand.

What We See In Practice

I work online, so it doesn't matter where my clients are, does it?

One of the most common misconceptions about the DTV is that remote workers can accept work from anyone while living in Thailand, including Thai clients and companies. However, the DTV does not permit holders to work for or provide services to businesses or clients in Thailand.
The DTV was introduced to allow digital nomads, remote workers, and freelancers to live in Thailand while working for employers or clients located outside Thailand. If you start working for a Thai company, provide freelance services to Thai clients, or carry on business in Thailand, those activities fall outside the scope of the DTV. In this case, you would need to obtain the correct visa, such as a Non-Immigrant B visa together with a work permit.
This is where many people get caught out. The DTV allows you to work remotely from Thailand for overseas clients, but it does not allow you to provide services to businesses or clients in Thailand. If you expect to work with both foreign and Thai clients, it is worth thinking about this before applying, as another visa may be a better fit for the way you plan to run your business.