Answer

Yes, traditionally one may take Navkarshi Pachkhan first and later take Ekāsanā / Ekāsanu Pachkhan, if one is sincerely able to follow the rules of Ekāsanā.

Explanation

• Navkarshi Pachkhan means taking a vow not to eat or drink until a certain time after sunrise, traditionally after reciting Navkar Mantra and observing the prescribed time.
• Ekāsanā / Ekāsanu Pachkhan means taking food only once in one sitting, according to Jain discipline.

So, if in the morning you first take Navkarshi Pachkhan, and afterward decide to do Ekāsanā, you may take Ekāsanā Pachkhan before eating, provided you can observe it properly.

Spiritual Understanding

Pachkhan is a sacred commitment of self-restraint. The important thing is that it should be taken with awareness, sincerity, and the intention to follow it fully.

Takeaway

You can take Navkarshi Pachkhan before Ekāsanā Pachkhan, but follow the exact method taught by your Guru Maharaj, Sadhviji, or local Jain tradition.