Netgear MR6500 AT&T renewed get only 4G.LTE when use SIM card 5G

Hi everyone,

Just received it today from amazon MR6500 AT&T unlock (renewed)

but with SIM card AIS 5G in Bangkok, Thailand. its only show 4G.LTE download speed at 4G (about 50 Mpbs by speedtest) but SIM card worked 5G super fast 400-500Mpbs on Samsung S22.

It seems that my new MR6500 can't reach 5G bands in Thailand or carriers outside US or not?

If anyone got the same problem like me or have any experience with that. I need your help and instruction to handle, please!

Many thanks.