Hi,
I am currently in Thailand on a 60 day (standard single entry) tourist visa but departing after about 35 days.
If I leave (probably going to Dubai) for a week then come back (via BKK), I am reasonable assuming they will stamp me in visa exempt for 30 days, and there won't be any issues as my 60 day existing visa won't be out of date at that time?
Many thanks
TLDR : Answer Summary
You can leave Thailand on your single entry tourist visa and return as a visa exempt traveler. After you exit Thailand, you will receive a visa exemption stamp for 30 days upon re-entry, unless you return after October 1st, in which case you'll receive 45 days. Your existing visa will not impact your entry, as it is single-entry and only valid for one initial entry.