ok I have found something that offers some info on this
New visa drama : from 30 days stamps to 15 days at land borders
Published 5 December 2008 Economy , Tourism
Here we go again… The forum ThaiVisa is hot like lava… The reason ? A new “visa drama” of course !
From time to time, the thai authorities love to toy with visa regulations… To change the rules… If possible without warning (it’s much more sanuk).
This new police order was issued on november 25.
But the “news” (in english) came only wednesday… In a way it’s highly ironic to see the thai police playing with visa regulations during a full blown tourism crisis…
By the way :
The TAT is also preparing an advertising campaign called “Apologies Thailand”, aimed at redressing the damage by the political turmoil and the Suvarnabhumi and Don Mueang airport closures. The agency will use the campaign to send a positive message to tourists around the world, encouraging them to come back to Thailand. (Nation) The TAT should talk to the police…
As usual, don’t try to understand. Because maybe there is nothing to understand. AKA : no conspiracy.
So what the new fuss is about ?
30-days border runs now only 15 days
In order to limit the amount of foreigners using “back-to-back” border runs, Thai Immigration has issued a new regulation regarding the 30 days tourist exemption.
Effective immediately, travellers without visa will get only 15 days of stay if they are arriving via a land border checkpoint from a neighboring country.
Passengers arriving via an international airport will obtain a 30 days stay, and for them there is no change.
This police order number 778/2551 is today confirmed by Royal Thai Police, Immigration Bureau, in Bangkok.
So if you’re a poor backpacker enjoying long trips and land borders, or a “visa runner”, you probably already found the link of the ThaiVisa forum.
Overall, there is without any doubt a political will to make it harder for foreigners who took for many years some liberties with laws…
The problem is : this will is often muddled, incoherent. And sometimes hypocrite too.
Anyway : times change.
UPDATE
Apparently, there are new regulations too for ” Extensions Of Non-immigrant Visas” (read here).