-"Gracias otra vez" or "Gracias de nuevo": These are very common and neutral ways to say "thanks again" in Spanish. They can be used in both formal and informal settings.
-"Le/s agradezco nuevamente": This is a more formal way to say "thanks again". It is often used in a business or professional setting.
-"Te/lo/la agradezco mucho": This is a very informal and expressive way to say "thanks again". It shows a lot of appreciation and can be used with close friends or family.