Yes, KINGDOMS is a Scrabble word!

Letter values in Scrabble US: K 5, I 1, N 1, G 2, D 2, O 1, M 3, S 1.

Is it a valid word?

KINGDOMS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a domain in which something is dominant
a country with a king as head of state
the domain ruled by a king or queen
a monarchy with a king or queen as head of state
the highest taxonomic group into which organisms are grouped; one of five biological categories: Monera or Protoctista or Plantae or Fungi or Animalia
a basic group of natural objects