In an evenly contested match that lasted two and a quarter hours, the Thai ace beat his Indonesian opponent 4-6 6-3 6-3 on Sunday.
Warit had five break opportunities in the first set but was only able to convert one of them and went a set down after Susanto broke serve on two occasions in the opener.
Boosted by five aces in the second set, Warit converted his only break opportunity to force the match into a decider.
The Thai player dominated the third set – which lasted 55 minutes – and broke serve twice, although he failed to convert as many as 10 break points before eventually forcing Susanto into submission.
The Thai women's doubles pair of Lertcheewakarn Noppawan and Wongteanchai Varatchaya won the gold medal when they beat Denise Dy and Katharina Lehnert from the Philppines in straight sets.
The pair from Thailand dominated the match from start to finish to win 6-3 6-4.
Dy did taste gold medal success later on in the day when she paired up with Treat Huey to win the mixed doubles title.
The pair from the Philippines triumphed 7-6 6-4 over Thailand's Plipuech Peangtarn and Ratiwatana Sonchat.