All of the documents they ask are pretty common, I think everybody needs to upload them. Make sure all is in English, upload any official tax document for last year, payslips, hotel confirmation, lease agreement from Thailand, all of your passports photo, letter from company where you are working, your CV/portfolio, bank statements in English, of you have your own company all of the company registration documents in English+ letter from your company to you + company portfolio.
You need to pay taxes only if you are in Thailand for more than 180 days per year. Actually banks started asking about your residencey(Kaskior) so it looks like "you don't need to pay taxes here" slowly ends
If you spend more then 180 days in the country, you can become tax resident in Thailand and pay taxes here. How it looks like in your country depends on the country and your specific situation. Talk with tax advisor in your country and later in Thailand