Yes, it is possible to have multiple accounts with ThinkMarkets.
You can for example have one or more other account types such as a Standard or ThinkZero trading account.
Once your account profile has been approved by ThinkMarkets, to create additional accounts login to ThinkPortal and select Create Live Account from the Quick Actions section. Here you'll be able to instantly create additional accounts.
You will be able to view all your Live Accounts via the Dashboard in ThinkPortal.