Carousell marketplaces are "country-specific," meaning you'll be able to browse, sell and buy on one marketplace at a time only.
The location settings in your profile determines the listings you'll see when you browse, and where your newly posted listings will be in.
For instance, if you change your city to Kuala Lumpur, Malaysia, you'll only be able to browse listings that are uploaded in Malaysia. Listings created by you after this change will also be in the Malaysia marketplace and priced in Ringgit (RM).
Unfortunately, existing listings that were created before changing your city will be placed in limbo, and will no longer be searchable in the either cities.