If an German national resident in Thailand holds UK listed equities in a US brokerage account, which DTA is applicable to the dividend income? Germany-Thailand, UK-Thailand or US-Thailand?

Thanks

Just a guess, but I would think it will be the DTA that matches your passport.

 

Otherwise people would try and use whatever DTA suited them best.

Or would it be where the tax was being paid or more to the point where you complete a tax return (if you do....)?

Germany-Thailand
 

I suppose you have been, or you still are, resident in Germany and never been resident in UK or USA.

 

The article 1 of your DTA says :

    This Agreement shall apply to persons who are residents of one or both of the Contracting States.