In the satire film, Tran is a supporting character and a Vietnamese political dissident who is jailed and "downsized" (shrunken to five inches, or 12.7 cm, tall) by her country.

Paul wants to join Dr. Asbjørnsen's plan of entering an underground vault to ensure the future of mankind but Ngoc Lan refuses, stating that the people above ground need help.

[2] Chau, who is of Vietnamese descent but grew up in the United States, worked on her character's accent by drawing from her personal experience with family members having been first-generation immigrants in the country.

[11] Alonso Duralde of TheWrap said, "If there's a standout here, it's Chau, taking a character who could easily have been a saintly martyr and making her funny, bristly, moving and occasionally profane.

[14] Among the mixed reviews, The Atlantic's David Sims said, "Chau's performance is energetic and heartfelt, but Ngoc Lan Tran seems to exist only to help Paul realize a truth about himself: He's not going to better himself simply by fleeing to a packaged 'perfect community,' and he needs to recognize the good in him to finally feel comfortable about his place in the world.

"[15] Time Out's Joshua Rothkopf said, "The introduction of a cringeworthy Vietnamese cleaning woman and ex-dissident (Inherent Vice's Hong Chau) borders on broken-English caricature.

[17] Emily Yoshida, writing for New York magazine's blog Vulture, said: Among the negative reviews, RogerEbert.com's Sheila O'Malley found there to be "a lot of problems" with the story and said, "Because Ngoc Lan is such a strong character, and Chau is so funny and strident and bossy, she takes over the entire film."

"[6] The Los Angeles Times said, "The character has also faced scrutiny from critics over the heavily accented broken English she speaks in a cadence that some say veers into stereotype before the script—and Chau's layered, dimensional performance—makes her a hero.

[26] Salon's John Semley wrote, "What the reaction to Downsizing['s Asian character] suggests are the real-world growing pains that accompany North America's increasing reliance on the arrival of non-European immigrants."

Semley highlighted a 2010 study that showed that participants found statements with "heavy Middle Eastern, European or Asian accents" were less truthful than those from native English speakers.

He said, "It seems reasonable enough to believe that viewers calling out Alexander Payne, or Thai-Vietnamese actress Hong Chau herself, as troubling or in poor taste are in fact dealing with their own built-in cognitive mis-recognition, as they struggle with internalized accent discrimination.

"[28] Literary critic Adam Mars-Jones said while films like Forrest Gump and Logan Lucky have "contorted messages that are sent when physically unimpaired actors occupy non-standard bodies thanks to the magic of special effects", the addition of Hong Chau as Ngoc Lan Tran to Downsizing was "putting this multiply marginal existence close to its centre".

[21] Vanity Fair wrote, "Chau steals every scene away from Damon and her other starry co-stars, including Kristen Wiig, Christoph Waltz, and Laura Dern.