If you're in the south and need to make a 30-day run to the Malaysian border, it's quite easy.
In Hat Yai, there is a large market/bus stop/song-taew stop on Petkasem Road about a 1/2 km from the downtown area. Underneath the pedestrian bridge that crosses the road there is a sign that says "Border".
A run to the border on a mini-van is 50 baht. This is a death-defying run.
Once you reach the border town of Sadao, you can hire a motorcycle taxi to take you through the border gates. This cost 100 baht and is quite efficient.
When you return from your run, stroll of the left-hand side of the street to the 7-11. In front of it will be someone to take your 50 baht and put you on a mini-van back to Hat Yai.
Easy peasy.