Not really, since under most (probably all) treaties, board member fees are taxable in Estonia. So where the work is performed isn’t all that relevant.
In general you are quite safe to pay employee salary for any work done in the business. If someone does a lot of work for the business (as defined by their board member contract) it makes sense to compensate them for this. This compensation should be classified as board member salary.
For most people reading this (who are mostly working in the business, rather than being a primarily passive owner with some board member duties), that portion of the work (and hence compensation) is usually negligible.
On a question on whether you’re “legally required to pay a board member salary, as a sole owner and board member” of an Estonian company (when also working as a regular employee), the EMTA replied this:
There is no such strict or clear rule about obligation to pay salary.
If payment is made finally, the taxation must be in accordance with the type of income.
So there’s no strict rule about a need to pay salary for board member duties. But if you do pay a board member salary (for duties covered by the board member contract), it will be taxed as such. If you only pay employee salary (for work covered by the employment contract), it will be taxed as such.