What is the 'letter from the education service' required for a Non-B visa in Thailand?

The user faced a refusal for a Non-B visa application due to the absence of a specific document referred to as a 'letter from the education service.' Despite confirming that they have the necessary documents from their university's HR, there is uncertainty regarding the exact nature of this required letter. Several comments suggest that this letter is likely from Thailand's Ministry of Education, confirming that the user should be issued a Non-B visa. There is also mention of challenges in obtaining the letter without the visa, creating a potential catch-22 situation. Additionally, users provide advice on reaching out to local contacts and specify the document as being linked to the Office of Higher Education Commission.