What are the requirements for the DTV visa application regarding the professional portfolio for digital nomads in Thailand?

They request one from me. That's what I did. Basically, I created a resume. I listed my job and duties. Then I pasted links that showcase my freelance works. Of there is no link of your works, just explain your job duties in details with whatever evidences that might support it. Also, include a LinkedIn link on that resume.

There are a lot of templates for many types of professional portfolio. So mine turns out to be just one page of PDF file with all those info and links. Will vary for you, of cuz. Good luck. I got approved.

I applied for DTV last month, Freelance consultant. HCMC, Vietnam. The consulate did request to see examples of my freelance work, and also evidence of freelance work coming up. They did also ask to see my CV, qualifications and professional portfolio. All of which was not a problem for me, and I successful in my application

Requirements vary according to the entry scheme you choose to apply for, as well as the embassy you choose to apply through.

What is your line of business, what do you want to do to work remotely in Thailand ?

The professional portfolio is an option, not a strict requirement, to prove one's freelancer status. Many of us have been issued a DTV without showing a portfolio. However, if your professional activity is such that you can provide a portfolio, show them one. If you are a graphic designer, a web designer, a translator, a SEO consultant, etc., providing a portfolio should be easy. In case providing a portfolio is impossible (because what you do can't be shown in a portfolio), then you can write a document in which you explain what you do.

Just book a qualifying cooking course. Keep things simple.