What tax rates are applied to payments of a gross revenue proportion?

Question

What withholding tax rate is applied to payments of a proportion of gross revenues by a Thai company to a UK school for ability to use its name and receive educational services?

A UK school contracts with a Thai company to allow use of its name and to provide services to create a school in Thailand with similar ethos and educational standards to the UK school.

It is paid fees in the development phase for assistance and thereafter a proportion of gross revenues of the Thai company operating the school. Is Thai withholding tax payable on these payments and, if so, at what rate?