Tonkin rhymes with:
conkin, conkin, dunkin, dunkin', hankin, henkin, jenkin, junkin, mankin, minkin, patinkin, punkin, rankin, thinkin, thinkin', younkin
Tonkin sounds like:
tangeman, tangen, tangney, tanguma, tankan, tanzania, tanzanian, temkin, teng-wen, tennessean, tennison, tennyson, tension, thinkin, thinkin', thomasina, thomasine, thomason, thomassen, thomasson, thomison, thomsen, thomson, tianjin, timken, timson, tingen, tinkham, tinsman, tomasina, tomasine, tomasini, tomasino, tomkin, tomson, tonnesen, townsman, townson, tunisian, tunison, twonshein