Do I need to be a resident of Denmark to apply for a Digital Nomad Visa (DTV) for Thailand?

Read the Thai Embassy of Copenhagen website.

Your questions are a little confusing - some information that might be helpful for you 1 - You only need a tourist visa to enter Thailand for a holiday - check the Thai goverment website for who can enter as a tourist Visa free. It is good for 60 days. 2 - A DTV Visa is something you apply for - it has a fee - it is offered in specific circumstances and documentation is as required by the Thai Government - again google Thai Government requirements for DTV Visa - if issued it is good for 5 years and multiple entries. 3rd - and what may be confusing you is the requirement to complete a TDAC - Thai Digitial Arrival Card - you do this online for any entry to Thailand - no matter if you are coming as a tourist or a Visa holder. So to sum - if you are coming as a tourist - depending on your passport you may not require any kind of visa - but do check - you do not say your nationality so no advice to give you - you can also check your country department of state who may have info. If you want to stay longer you should explore visa options - and no matter how you come, how long you want to stay, what visa you have or do not have you must complete the DTAC no earlier than 3 days before your arrival

What's your question a) Whether you can enter Thailand visa free using a Danish passport or b) whether you can apply at the Thai Embassy in Denmark without being a Danish citizen or resident? According to the embassy (see below) you need "proof of residence" if you want to apply for a visa from Denmark.

You can apply at any embassy as long as you met the requirements