Are 3 month tourist visas one use only? For example, could I have been here for 2 weeks, fly to Europe for a month and enter Thailand again for the remainder of my visa?
TLDR : Answer Summary
Most tourist visas for Thailand are issued as single entry, meaning once you enter Thailand, the visa is marked as used and can't be used again for re-entry. To leave Thailand and return while still under the same visa, one could apply for a re-entry permit, allowing them to continue their stay within the original visa's validity. Alternatively, for those eligible, a visa exemption can grant a new permit upon re-entry.