While I don’t know the details of Thai work permit requirements, I have worked for multinational corporations in remote countries.
By far the easiest way is to become an employee of the local subsidiary. Most multinationals will have a subsidiary to at least support their local sales team. There will be internal processes to move budget to support someone in a division that may not currently exist in the subsidiary, but that is usually not too complicated.
Becoming a local employee of a subsidiary usually makes the issues around a WP easier, as the subsidiary likely has a number of local employees and a sizable investment in the country. Although one negative factor may be that you will be put on the local pay scale and local benefits, which may be less than the home package.