Can I apply for the DTV visa in Thailand if I earned income as a freelancer during my tourist visa stay?

You should not face issues applying for the Digital Tourist Visa (DTV) after having freelance income during your previous stay on a tourist visa in Thailand. The key point is that your income must be from clients outside Thailand and you should not have worked for local Thai clients or operated a business within the country. As long as you can prove that your work was done online for foreign clients, you should be eligible for the DTV.