Applying for new Passport, but still using current?

[acenase]

My US Passport has quite a lot of small spaces on earlier pages because I'm sure a lot of you can relate that when you travel immigration skips over pages to stamp a random blank page. But I quickly realized when I started to do border run to Laos, their Visa takes up one full page, and the Thai visa also takes up a full page, I don't have any more spare full pages to givs up for another Visa, but I still have many spaces for Entry/Exit stamps (About 8 spots big enough for entry/exit stamps), so my question is, if I apply for a new US Passport at Embassy in Thailand, will I get to keep my old passport to use for places that just require a stamp and use my new Passport to insert the full page Visas? Or once I apply for a new Passport, they will take my old Passport or Void it so i can never use it?  Seems like a waste that I can't fill up all the empty spaces on the pages that don't require a Visa, and as many of you know the US embassy stopped selling additional pages since last year. So what would your recommendation for me be? 

[ubonjoe]

They will stamp your old passport as canceled and punch a couple of holes in the cover to show it has been canceled when you pickup your new passport.

Your new passport will have 52 pages which may last longer than your current one.

[tonray]

You can also apply for a second passport. When I renewed she asked me if I traveled a lot and if so perhaps a second passport would be useful. I don't know the requirements but she seemed to be pushing them at the time.