Can I transfer my visa to a new passport in Thailand and what issues might arise during travel?

A friend of mine is in the middle of some traveling and she's had to get a new passport. She still has a valid visa extension in the cancelled passport that she's carrying with her (as well as the new passport).

Can she only transfer the visa to her new passport at the same immigration office that issued the extension?

If she does a stopover in Thailand on a weekend, goes to another country, then returns to Thailand in a few weeks will that cause any issues?

I'd appreciate any help from someone who has similar experience.

Thanks.