Do I need to report back to immigration after re-entering Thailand from Vietnam?

After re-entering Thailand, you need to report back to immigration if you are not staying at a hotel; this is done through filing a TM30. If you're considering a tourist visa extension, it's also advisable to handle the TM30 at that time, as it's often checked during extension applications. Many users have reported that the immigration office in Pattaya is accommodating, and in some cases, no fee is charged for the late report.