You don't need a lawyer for a will anywhere.
All they do is ensure that the document follows the local conventions, which can be done by yourself for free. It is quite a simple format. i have this, I want it to go here. Sheesh, how hard is that to fuck up.
Thai stuff, Amphur, international stuff, properly formatted and witnessed document according to your countries laws which are easily searchable. the only benefit of a law firm is when you want them to act as executor, which you pay for.