Depends on your entry method. With a long term visa it should be no problem. Off a tourist or visa exempt entry almost impossible without the help of an agent.
Anonymous participant 205 No idea where you got that from. In Phuket if you stay in a hotel or hospital (even in Phuket) you need to re-file a TM30 for your actual residence.
You must report being 90 days in Thailand. The fact that you’re allowed up to 7 days after to do so is irrelevant. If you don’t report you may be subject to a fine when you next interact with immigration.