Are Immigration Rules Laxer In The South?

I'm back in Pattaya (well, almost) from my first trip south of Hua Hin. I won't name the places in order not to attract unwanted attention to the people I'm going to mention, but let's say I went to two popular islands in the south.

One thing that struck me were the number of Westerners who are working in the South of Thailand, in plain view, performing jobs that are normally restricted to Thais. I have seen Western guys and gals working as greeters at restaurants, flipping crepes in a mall or working as front desk people at fancy hotels, which is something that you almost never see in Central, Eastern or Northern Thailand.

Are there different rules regarding the employment of foreigners in those provinces or are immigration officials simply more zealous when it comes to enforcing existing rules in the north?