Signage for the Stock Exchange of Thailand (SET) is displayed outside the bourse in Bangkok, Thailand, on Monday, Oct. 26, 2020.Taylor Weidman | Bloomberg via Getty ImagesSINGAPORE — Investors may be shying away from markets in Southeast Asia, but JPMorgan’s James Sullivan sees opportunity in the region over the medium term.”We’ve upgraded Indonesia, we’ve upgraded Thailand on the argument that investor positioning in these markets is incredibly light,” Sullivan, head of Asia ex-Japan equity research at the firm, told CNBC’s “Squawk Box Asia” on Thursday.”We’re looking at opportunity for over $650 billion in overall asset flow into emerging markets generally. In ASEAN, for the first time in many, many years, investors are underweight every single ASEAN market,” Sullivan said, adding that the region will be “interesting … from the reality versus perception perspective.””We do see … significant opportunities for medium-term outperformance, specifically in ASEAN,” the analyst said.So far in 2020, markets in Southeast Asia have largely been among the worst performing. Multiple economies in the region are either struggling to manage the coronavirus pandemic or grappling with the loss of important tourism dollars as restrictions curb international travel.As of their Wednesday close, the SET Composite index in Thailand had fallen more than 10% year to date, while Indonesia’s Jakarta Composite has declined more than 9%.The best market performers in Asia this year have generally been manufacturing-driven economies in North Asia, which Sullivan said are looking positive in the longer term.”From a global economic perspective, what we’re seeing is really a two-stage or a two-speed recovery,” he said. As data continues to show a “very constrained” services sector globally, manufacturing has “come back very well.””We’re looking for outperformance on an overall economic basis of China and … some of the North Asian markets,” Sullivan said. “On the longer-term basis, we still see the manufacturing driven economies of China and North Asia looking very good.”Subscribe to CNBC PRO to access live PRO Talks, including our Dec. 2 discussion on opportunities and risks in international markets.