Left with single testicle

Can right testicle in a superficial position produce mature sperm. Left testicle was removed, it was undescended
 
I don’t know what you mean by your description of your testis. A single testis is sufficient to produce enough sufficient sperm to achieve fertility. However, whether your remaining testis is producing sufficient normal sperms can only be determined by doing a semen analysis. This test will be able to confirm that for you. An undescended testis on one side is usually associated with incomplete descent on the other side. Incompletely or undescended testes do not achieve the cooler temperatures required for normal production of sperms. I would advise you to consult a qualified doctor and undergo this test.