Thai Forest tradition: thoughts like rain drop

Q: There is reference in the Thai Forest tradition to a teaching given to sāriputta by Buddha of thoughts like rain drop bubbles rising the mergie into the body of water?

A: Sāriputta enlightened as sotāpanna in Vinaya. Mahā (1) Mahākhandhaka, then he enlightened as arahanta in Sutta. Ma. Ma. Dīghanakhasuttaṃ, which it's atthakathā gave the similitude of vedanā arising and vanishing as bubbles.

Another, In sāriputta's cannons, KN Cūḷaniddeso Mogharājamāṇavakapañhāniddeso, used the similitude of viññāṇakhandha as bubble as well.

So, sāriputta maybe one of monks who listening Phena Sutta (SN 22.95), then he described his arahanta-enlightening-moments to his students. Then at 1st saṅgāyanā, his students put his description into that ancient atthakathā and into that KN Cūḷaniddeso which authored by sāriputta.

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Also, in KN Dhammapada's atthakatha Dha.A.6 atta-kodhavagga Buddhavaggavaṇṇanā 2. Yamakappāṭihāriyavatthu. (149), there are the sāriputta's conversation with the buddha about he is a genius who can count every rain's drops into the ocean, mountain, and the ground.