Portfolio is basically to demonstrate in more detail your online work. I included an outline of what wo/tasks are done online, company remote work policy, emails of appreciation from clients, company background, website links, letter from employer that i work remotely and they support my DTV application etc.
You do not need 500K a month to apply for the DTV, just 500K THB in a personal account. Depending on the embassy you apply at no seasoning is needed or up to 6 months. is required
You can find some experiences in the main DTV group on FB. This year, non permanent residents/ citizens were allowed to apply from Japan. Im a long term resident in Japan but applied in Taipei last Dec due to the permanent resident only rule in place at the time. Make sure you give solid reasons for the 5 year visa, Tokyo Embassy has issued a few 6 months METVs instead of the DTV.
My bank statements are in Japanese. Transactions descriptions and amounts, my address all needed to be translated into English as per Taipei embassy requirements. The embassy required original and translated versions.
The 3 month seasoning of 500K depends where you apply, Laos requires 3 months but many embassies are ok with just a final balance of 500k with no seasoning and several months of statements. It must be in a personal bank account, It is ok to show business income without you in receipt of a salary at the moment, others have done similar and got approved.