The Thai eighth seed, who also won the tournament in 2016, defeated Tokyo Olympic champion Chen Yufei of China 21-15, 13-21, 21-16 in 65 minutes to win the BWF World Tour Super 750 event at Axiata Arena in the Malaysian capital.
The 26-year-old took home the $47,250 (1,630,000 baht) winner's cheque while Chen received $22,950 (791,000 baht)
Ratchanok, who won her last title at the Indonesia Masters in 2020, received a congratulatory message from Thai badminton chief Khunying Patama Leeswadtrakul.
"I would like to congratulate May [Ratchanok's nickname] for winning the Malaysia Open title. This time she beat reigning Olympic champion Chen Yufei, the fourth ranked player in the world, who has won 15 times in their 17 meetings," she said.
"This time May is in great shape both physically and mentally. She did very well today, especially in the third game.
"She finally was able to beat Chen in the title match after losing to her in three finals [the 2019 Toyota Thailand Open, 2019 Hong Kong Open and the 2022 Indonesia Masters]."
Dechapol Puavaranukroh and Sapsiree Taerattanachai were unable to complete a double for Thailand after the mixed doubles pair went down to arch-rivals Zheng Siwei and Huang Yaqiong of China 13-21, 18-21 in the title match.
The men's singles crown went to top seed Viktor Axelsen after an easy 21-4, 21-7 win over second seed Kento Momota of Japan in the final.
It was the third straight title for the 28-year-old world No.1, who won the Indonesia Masters and the Indonesia Open in Jakarta last month. The Dane also won the All England Open title earlier this year.
Apriyani Rahayu and Siti Fadia Silva Ramadhanti of Indonesia took the women's doubles crown with a 21-18, 12-21, 21-19 victory over Zhang Shuxian and Zheng Yu of China. Second seeds Takuro Hoki and Yugo Kobayashi of Japan were the men's doubles winners, beating sixth seeds Fajar Alfian and Muhammad Rian Adrianto of Indonesia 24-22, 16-21, 21-9.
The Malaysia Masters starts tomorrow in Kuala Lumpur.
