Because of Thai law enforcement. Foreign filmmakers are enforcement to hire a local coordinator (company or individual) who is officially registered with the Thailand Film Office, Office of Tourism Development. Each coordinator must represent the foreign filmmaker for obtaining any necessary permits. Local coordinators are also responsible for representing the film company in any matter arising both during and after the completion of shooting in Thailand. The permission must be allowed before the shooting start.
Thailand coordinator Filming Services included;
Local Coordinating for filming project in Thailand