Write once memory (WOM) codes allow reuse of a write-once medium. This paper focuses on applying WOM codes to the binary symmetric asymmetric multiple access channel (BS-AMAC). At one specific rate pair, WOM codes can achieve the BS-AMAC maximum sum-rate. Further, any achievable rate pair for a two-write WOM code is also an achievable rate pair for the BS-AMAC. Compared to the uniform input distribution of linear codes, the non-uniform WOM input distribution is helpful for a BS-AMAC. In addition, WOM codes enable “symbol-wise estimation”, resulting in the decomposition to two distinct channels. This scheme does not achieve the BS-AMAC maximum sum-rate if the channel has errors, however leads to reduced-complexity decoding by enabling independent decoding of two codewords. Achievable rates for this decomposed system are also given. The AMAC has practical application to the relay channel and we briefly discuss the relay channel with block Markov encoding using WOM codes. This scheme may be effective for cooperative wireless communications despite the fact that WOM codes are designed for data storage.