Letter Of Approval From Govt - Timeframe?

How long does it usually take to get the "Letter of approval from government agencies such as the Office of the Private Education Commission, the Office of the Basic Education Commission." My first time applying for a B Visa, so I'm not too up on the play regarding time frames etc.

The school I'm going to be teaching at next year said they had to "send away to Bangkok" for the letters of approval etc, but they seem to be taking quite a while (more than 1 month so far I think, not sure exactly though as my updates on the process are few and far between).

But yeah, is this something which is a 1 month thing? or more like a 2-3 month thing?

Just wondering if I should plan a trip back to Laos for another tourist visa (if it's likely to take a while), or if I should just do the 30 day extension in Khon Kaen and then goto Laos when my letters arrive. As I want to avoid too much pissing around / long bus rides if possible.