When it is

AbilWhen it is 10 o'clock in the morning in India, it is 12:30 pm in Seoul and 10 pm (?) in the USA.

Is this correct and natural way to say? Thanks.

This is fine except that you need to specify which time zones you are talking about. The U. S. has five (or is it six) counting Hawaii. I don't know about the other countries you mention.

Thanks Ray H. I am talking about local standard time.

Abillocal standard time

Local standard time varies minute by minute as you move across the globe from east to west. Each country covers a large territory, so each country has an infinite number of local standard times. I'm sure you don't really mean 'local standard time'.
If you chose a specific city in the U.S., your statement would make more sense.

Sorry, I did not know that the USA has many local standard times.

Oh, yes! In Los Angeles it's 8 pm and in New York it's 11 pm, for example. In Denver it's 9 pm, and in Chicago it's 10 pm. But in Honolulu it's 3 pm!

Thanks CJ