Shoppers noticed this week that they cannot check out if their order is less than VND887,000 on the Temu app.
Those who had bought for more than VND1 million were informed they had exceeded the limit and had to remove some items.
Hieu, an online shopper in HCMC, said: "This policy and the requirement to pay in advance make the platform less attractive compared to its competitors in Vietnam."
When Temu first came to Vietnam at the end of September, it required a minimum order of VND120,000.
It raised it to VND632,000 last week and to VND887,000 now, a sevenfold increase in two months.
Temu said the minimum allows it to "continue offering more and lower-priced items."
Although it did not explain why the cap was set at VND1 million, one obvious explanation is that there is no tax on e-commerce items under this price.
But with an estimated 4-5 million such items shipped from China to Vietnam every day, the government has been considering scrapping this tax waiver.
Temu says on its app that it is in the process of registering with Vietnamese authorities.
Government officials have warned that all unregistered e-commerce platforms will be blocked in the country.
Temu, formally owned by Singaporean company Elementary Innovation Pte. Ltd., reported zero revenues in its third quarter financial disclosure submitted to Vietnamese tax agencies, and said it expected to record revenues starting in October.