"The biggest winner will be Vietnam as foreign investors start to flood the country. Number two might be Malaysia and number three is Japan," Deborah Elms, executive director at Asia Trade Centre, told CNBC on Tuesday.
The Peterson Institute of International Economics (PIIE) echoed Elms in a recent report, citing tariff-free access to U.S. markets for apparel and footwear, Vietnam's top exports, compared to the current 17-32 percent tax range.
That's expected to boost exports to the U.S—already Vietnam's largest export market—and dramatically increase foreign direct investment inflows in a country with the lowest per capita income among TPP members.
PIIE also notes that Vietnam would see the largest percentage income gains and export increases out of all countries at 13.6 percent and 31.7 percent, respectively.
Malaysia does not yet have bilateral free-trade agreements (FTAs) in place with the U.S., Canada or Mexico, so it should be another key beneficiary of a TPP agreement.
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"The TPP deal would provide Malaysian exporters with enhanced access to the entire North American market, and would also improve Malaysia's attractiveness as a hub for North American investment inflows," Rajiv Biswas, Asia Pacific chief economist at IHS, said in Tuesday note.
For Japan, the opening of services markets is a major advantage, explained Elms of Asia Trade Centre. A TPP deal would open the services markets of each member nation to one another, and because Japan's services sector is relatively uncompetitive, it has a lot of room to grow, she said.
"That means all kinds of services markets that have been problematic for foreign investors to penetrate should be open, including logistics, distribution and warehousing, as well as travel, tourism, and food and beverage."
Moreover, the combined impact of the TPP and a potential FTA with the European Union could substantially lift Japan's long-term growth rate, according to Biswas.