Yes, SOYMILK is a Scrabble word!

Letter values in Scrabble US: S 1, O 1, Y 4, M 3, I 1, L 1, K 5.

Is it a valid word?

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

a milk substitute containing soybean flour and water; used in some infant formulas and in making tofu

Also: soya milk, soybean milk.