Mommy's question what do u do to make your 21 month old stay in his bed my son keeps getting out of…

Mommy's question what do u do to make your 21 month old stay in his bed my son keeps getting out of bed constantly and won't stop I keep putting him in bed without saying a word and its never ending he laughs about it when he sees me and runs and try to run back into bed and when I walk out he is back outta bed again heeelp.....