Thai language class for foreign teenager in Phuket

Looking for recommendations on where to have a German teenager learn Thai in Phuket without prior knowledge.

The teenager is a dual Thai / German citizen who went to school in Germany for 6 years and can also read/write and communicate well in English.

An in-person course / class would be best as opposed to a private teacher, for the purpose of also making friends and being around people. South of the island preferred.

A Thai government school or a private school isn't really an option at this time, as the family needs to be able to travel even on short notice. So there should be no rigid schedule, pressure to not miss classes or tests. The focus would be purely on the language, not on other subjects.