i have return flight aug bkk dublin can icancell or change it or get voucher? will i be charged?

If it is a standard ticket you should be able to change the date once for free or get a voucher.

Change to any time in the next 2 years free of charge and few other options.

 

https://www.emirates.com/ie/english/help/keep-your-ticket/

 

You can change or cancel for free if the reason is one of those listed below.  If not your ticket rules will apply.

 

• Flight Cancellation: Emirates flight is cancelled for a specific date or route is suspended for a continuous period of time
• Travel ban: Where there is an explicit government notification that prohibits travel from either point of journey origin or  destination
• Travel advisory: A general government advisory against non-essential travel but no travel ban
• Visa process change / Quarantine: Visa process which required visiting an embassy/consulate OR mandatory quarantine at origin or destination
• Passenger is unable to reach airport:   Countries which have a government lockdown and passengers are unable to reach airport