Hi @phitran, i’m using TTN in Hong Kong, same frequency plan AS923-925 (“AS2”).
This is my gateway config:
And my end device:
I use the LMIC library with #define CFG_as923 1
This works well, and my gateway sees other non-TTN uplinks (923.2-924.6MHz) so i think this configuration is correct.
Hi Mr. @jreiss,
I am using The Things Stack with v3.15.5 and I can’t find the right frequency option. Is there any limitation with this version?
Currently TTS(CE) (aka TTN V3) running on 3.22.2 so you are somewhat behind wrt maintenance & updates/features/compliance/security etc. and would recommend you update, irrespective of freq plans 
Hi Mr. @Jeff-UK ,
Thanks for your advice.I have updated to V3.20.0 version. Selecting AS923-2 has appeared but I am having a similar error in the link below. I have read the comments and have not found the solution yet.
As this is a double post but the other is more relevant, closing this thread.