I have only one 60 days thai visa stamp in my new passport and I have only used 33 days of that stamp and want to enter Thailand after leaving for 7 days. (I am allowed to stay 30 days without visa). Will I have any problems with that?
TLDR : Answer Summary
The user has a 60-day Thai visa stamp valid for a remaining 27 days and plans to leave Thailand for 7 days before re-entering. Advice given in the comments indicates that although a new passport does not erase entry history, and that the Thai Immigration Officer has discretion over admissions, it may be possible to re-enter under the 30-day visa exemption. Additionally, obtaining a re-entry permit could keep the existing visa active, allowing re-entry without losing the previous stamp.