Here in Jomtien immigration , they give you up to one week to register the address then the fine is 1600 baht. You can register online your address when you arrive in Thailand, you only need to go to immigration to get a TM30 for an extension and that's how you could get fined. If they ask you so much money , just do a border run(60 days) instead of an extension(30 days).
******************************************************************************************************