@Stuart ********
The first part of your statement is accurate - from the US perspective, the emergency passport is just a smaller, shorter validity version of a regular passport. Most countries, including Thailand, are fine with that, but I did see a YouTube video in which a guy was refused a visa to India because they wouldn't put it in an emergency passport.
The second part of your post isn't really accurate, though that's not important to the OP. In almost every case where a US citizen is limited to direct return to the US (e.g., an extradited prisoner, or someone given a repatriation loan), that's done with a limitation endorsement in a regular passport. I've seen travel letters issued for prisoners under escort, but that's rare (since many countries won't accept them for exit or transit).