For Shri Neminath Bhagwan (the 22nd Tirthankar), a simple and respectful chant is:

ॐ नमो श्री नेमिनाथाय Om Namo Shri Neminathaya

Meaning: “I bow to Lord Shri Neminath.”

A common Jain devotional chant is also:

णमो अरिहंताणं Namo Arihantanam

This is a universal Jain mantra, and it can be used for devotion to all Arihants, including Shri Neminath Bhagwan.

If you want a short jap for daily chanting, you can repeat:

ॐ नमो श्री नेमिनाथाय

with bhakti, shuddha bhav, and ahimsa in mind.