You are only working on one degree at a time. However, it should be noted that an associates is kind of a weird degree in that it's really just a degree that signifies that you finished the first two years of a bachelor's. Honestly, I'm not entirely sure what the purpose of it is beyond that-- probably so that you have something to signify that you've finished the coursework offered at a 2-year institution. At 4-year schools you complete the exact same coursework in the first two years but don't get an associates. and associates is literally just the first half of a bachelor's degree.

A master's on the other hand is totally different than a bachelor's and you earn it completely separately from a bachelor's (although you have to finish the bachelor's first) if you want to get a master's. There are special programs where you can work on master's coursework while you are getting a bachelor's, but this is an exception and not super common.