While doing research for the Lotus Roots Project, I came across web sites and documents that show Chinese from New Orleans participating in the Civil War in both the Federal and the Confederate side.
In all I have located nine Chinese from New Orleans who served on the Union side and possibly five that served on the Confederate side. The actual number could be considerably higher especially on the Confederate side, since the Confederate records did not survive as intact as the winning federal side.
More information will be forthcoming. In the meantime, you can browse links provided and learn more about Chinese particiaption in the Civil War and WWII.