What are my options for applying for a business visa in Thailand while residing in Europe?

I hope someone can help/advice

I been living in Thailand for 15 yearsworking for a company with a workpermit

in 2020 I open my own company and left Thailand to get a business visa then the covid started and I couldnt get back in and stayed here in Europe to wait

Now its open up and want to do the steps to get the visa but I am not registrate here in Europe (I have a dutch passpoort and staying in spain now)

I read in many post that they require you have to proof your citizenship of the country where you applied

I really want to apply it in Belgium as there I be taken off back to Thailand

In the past there was no problem, you could even go to the neighbore country like Singapore or Malaysia to do you visa

Does any one know what can be done

or shall I go with a Tourist visa to Thailand for later to go out again and apply the visa in Singapore

Thank you