The 11th ranked Thai, who was seeded sixth in Birmingham, went down to world No.4 Okuhara 21-12, 21-16 in the 44-minute women’s singles decider at Utilita Arena.
It was Okuhara’s fifth win against Pornpawee in six meetings.
With the victory in yesterday’s decider, Okuhara, 26, claimed her second title at the sport’s oldest tournament. She won her first All England Open crown in 2016.
She also completed a hat-trick of wins against Thai players at the BWF World Tour Super 1000 event. The diminutive Japanese beat Busanan Ongbamrungphan in the quarter-finals and Ratchanok Intanon in the last four.
The Japanese also dominated the doubles events as all three doubles finals were all-Japanese affairs.
Hiroyuki Endo and Yuta Watanabe defeated Takeshi Kamura and Keigo Sonoda to lift their second straight men’s doubles title.
Endo and Watanabe, the world’s sixth-ranked men’s pair, defeated their fifth-ranked opponents 21-15, 17-21, 21-11 in 68 minutes.
The women’s doubles crown went to second seeds Mayu Matsumoto and Wakana Nagahara who defeated top seeds and defending champions Yuki Fukushima and Sayaka Hirota 21-18, 21-16 in 56 minutes.
Unseeded Yuki Kaneko and Misaki Matsutomo and second seeds Yuta Watanabe and Arisa Higashino were due to meet in the mixed doubles decider.
Second seed Viktor Axelsen of Denmark, the 2020 champion, and sixth seed Lee Zii Jia of Malaysia were due to meet in the men’s singles championship match.
World No.2 Axelsen entered his seventh straight final while the 10th ranked Lee claimed the week’s biggest scalp in the form of top-ranked Kento Momota in the quarter-finals.
Axelsen ended the 21-year wait for a Danish men’s singles champion when he won the title last year.
With the tournament not counting towards Olympic qualification, leading Asian badminton nations China, South Korea and Taiwan had opted not to travel because of COVID-19 restrictions.
Indonesia’s team were forced to withdraw from the tournament earlier this week after a passenger on their flight to Britain tested positive for the coronavirus.