Yes, interesting about goods. But about services it does say if the services are provided outside Panama. If OP works in Panama that eohld not be the case.It is also possible that the Panamanian lawmakers do not understand the definition of foreign source income. According to this article, which seems well-researched, those Panamanian lawyers cited by nethostler appear to be correct.
Panama has a territorial taxation system that levies taxes only on operations that take place or that have effects within the country’s territory. Income tax, in particular, is levied only on income that arises from a Panamanian source, regardless of the nationality or residence of the income...oxfordbusinessgroup.com