Can I return to Thailand with both my old and new passport if I get a new passport while visiting the UK?

The user is in the UK with a Thai work permit and is considering obtaining a new passport. They are asking if they can show both the old and new passport upon returning to Thailand. The comments clarify that while the work permit is not in the passport, it is suggested to ensure proper visa transfer procedures when getting a new passport, as work permits and visas are typically handled separately.