I understand that Hull will now only issue a single-entry Non-B for an applicant taking up employment in Thailand. Is this actually the case? The supporting documents download from their website also says in addition to the sponsoring company's letter that "Such company must provide evidence that it is registered in Thailand."

One of our French Consultants picked up a multi-entry Non-B at the Cardiff Consulate earlier this month with just the standard supporting letter from the Thai employer. It was also done as a walk in customer, while he waited after making an appointment.

From this I assume that it is just Hull that has tightened their rules?

It seems that each consulate has it's own set of criteria, something which shouldn't be a surprise to someone who has lived in Thailand!

Many years ago I used to apply to Liverpool Consulate for the non-B and they accepted a letter from the company until they introduced the additional requirement to have a confirmation letter faxed to them from the company office in Thailand.