It's not inherently racist, but I would conjecture that these puns occur more frequently with Asian names (unfortunate spellings are pretty popular e.g. Phuc, Bich, Wang, etc. despite pronunciation being completely different). One factor is probably due to their rarity in comparison to Anglo names.
It results in terribly tasteless, low-brow "jokes" such as https://www.youtube.com/watch?v=CaOkTKfxu44