When you have diabetes excess sugar (glucose) builds up in your blood which then causes frequent urination, which may leave you dehydrated.
So yes being constantly thirsty even at night is a common diabetes symptom so if you're constantly thirsty either during the day or at night then it could be possible that you may have diabetes or may be developing diabetes.
So it's best to go to the doctor to get tested for diabetes and let the doctor know that you're thirsty during the night so they can find out exactly what is causing it.
Sometimes though you might just be drooling at night and drying your mouth out which makes it seem like you're thirsty due to a dry mouth.
I sometimes wake up in the morning with a very dry mouth and it's just because I drool sometimes a lot at night so I become thirsty and have a dry mouth.
But being thirsty at night and during the day can sometimes be a sign of diabetes so it's best to get tested for diabetes just in case.