Like many others already said, if you tell the reception your problem, they will send you to a specialist. If you know what sort of doctor you need to see, you book one online.
You can ask you HR or Finance department to help with your yearly tax declaration, done between February - April. On that tax form you can declare your Estonian income besides your Thai income. Then you will get a paper from the tax department what tax you still need to pay. This can be done in one go or you can pay equal parts in 3 months time.
It would be nice if you actually read his comments:
"She could apply for a non-o visa at a nearby embassy or consulate with supporting documents from the organization." So she can do both.
As per Ubonjoe: "the total period of stay shall not exceed one year from the date of entering the Kingdom."
So need to leave the country to get a new visa.
Dividend's are paid to shareholders unless your Thai company is a shareholder of the Estonian one his suggestion is not the right one. You as a share holder can get paid dividend on a private account there, pay tax in Estonia and take money out of that account with an Estonia bank card. Salary could use the same process.