Hi, you might want to refer to resources for regex like https://stackoverflow.com/questions/38615740/regular-expression-to-accept-all-thai-characters-and-english-letters-in-python. You can also try some regex testing tools like https://www.regextester.com/116401.

The following answer is from ChatGPT, do try it in future for yr technical questions if they are generic programming questions:

The following regular expression should satisfy your requirements:

regex
^(?!_)[\x20-\x7Eก-๙0-9_]{1,250}$

Explanation:

• ^: Asserts the start of the string.
• (?!_): Negative lookahead assertion to ensure that the filename does not start with an underscore.
• [\x20-\x7Eก-๙0-9_]: Character class that allows ASCII characters (excluding control characters), Thai characters, numbers, and underscores.
• {1,250}: Specifies that the length of the filename should be between 1 and 250 characters.
• $: Asserts the end of the string.

This regex allows ASCII characters (excluding control characters), Thai characters, numbers, and underscores. It ensures that the filename does not start with an underscore and enforces a maximum length of 250 characters.

Thank you very much for this.  We got it working.

Thank you very much for your guidance pointing us to the right direction.