Hi, I will reach Guilin airport on 13 dec 12pm. Please advise how to get to nanning by speed train.

Hey, at that time there is no train running to Nanning.
You’re suggested to stay near the airport for one night and go to the railway station the next morning.

Take airport shuttle bus to GL Railway Station (Shanghai Lukou), where high speed trains run to Nanning from 06:55 to 20:55.