It is any wonder that any Thai 'qualifications' are not trusted by overseas universities or companies? I believe that US universities insist that Thais take an entrance exam, no matter if they 'appear' to be qualified.
And I know a secretary who worked for a prestigious school in Sydney at which a couple of Thai brothers were studying. They failed their exams, insisted they be given passes otherwise Daddy would remove them and their fees from the school, and the school waved them goodbye.
My wife also studied at a Bangkok university to teach English. She showed me an exam paper she was given, and on just one page there were around 15 errors. I corrected the paper, she gave it to the professor, who simply threw it in the bin.