Can I register a Thai company while I am on a tourist visa?

Yes. A tourist visa does not automatically prevent you from registering a Thai company. However, registering a company is different from working for it. If you intend to manage the business or carry out work in Thailand, you will normally need the appropriate visa and work authorisation before those activities begin.

What We See In Practice

If I'm on a tourist visa, does that mean I can't start a business in Thailand?

Many foreign entrepreneurs assume company registration and immigration status are the same thing. In reality, you can often incorporate a company while visiting Thailand, but a tourist visa does not give you the right to work for or operate that business once it has been established.
Registering a company is a corporate process, whereas your visa determines what you are personally allowed to do while you are in Thailand. A foreigner can generally become a shareholder or director of a Thai company regardless of holding a tourist visa, provided the company satisfies the relevant corporate and foreign ownership rules. However, once you begin managing the business, meeting clients, supervising employees or carrying out other work-related activities, the correct visa and work permit will be required.
Many business owners discover that the practical challenges often arise only after incorporation. Opening a corporate bank account, applying for a work permit, and switching to the appropriate business visa typically require a different immigration status. In practice, banks also generally do not open business accounts for holders of tourist visas.