No.
Hong Kong is a natural entrepot for the south China area. Memel isn't for the Baltic. Any trade can go out any number of ports. So it lacks one important long term advantage.
Mao and the PRC found Hong Kong useful. It required food and water from the PRC and thus was one of the few sources of hard currency for the PRC. The Soviets have plenty of other sources. Why would they tolerate Memel if they don't need to do so?
Relatedly, Hong Kong also allowed PRC to have a window to the west. Given its diplomatic isolation, Beijing found Hong Kong useful to pass on messages when needed. The Soviets already have diplomatic relations with much of the world.
For most of the post-World War II period, Hong Kong wasn't a port used by the PRC which shut itself off from economic contact with the West. It industrialized as a result of Chinese refugees with useful skills who rebuilt their businesses in Hong Kong and shipped Hong Kong goods overseas and imported the raw materials. It didn't actually ship PRC goods out. That didn't begin until Mao was dead and Deng Xiaoping opened up trade. That was thirty years later.
So Memel won't be serving any of the needs for the Soviets that Hong Kong did for the PRC.
But let's try to work out a POD.
The only way for Memel to thrive would be for it to avoid participating in WWII at all. Neither the Nazis nor Soviets occupy for it for some reason (almost ASB - but perhaps Memel is used by Germany as a place to exile Jews, and thus the Nazis don't want it when they could grab it. When the Final Solution comes about, instead of invading and deporting them to the camps, they believe they can just starve them out by sealing them off - but Memel barely survives through Swedish imports of food). The Soviets agree not to occupy Memel on their drive to Berlin and respect their neutrality in order to not provoke Washington and London.
Refugees flee to Memel after WWII to escape communism, bringing with them essential skills that allows them to resstablish their businesses in Memel. Stalin, inexplicably, allows this to happen - perhaps out of a concession to the US for a place to free Poles (and Balts) in the West to retire to since he won't let them into Poland or let the Baltic States be independent. However, the area quickly becomes walled up so that people can't flee to Memel to escape Communism (like what was eventually done in Berlin).
Memel does possess a variety of odd skills from a combination of its native population, displaced Jews, returning Polish and Baltic exiles from the West, and whomever could escape there from Communism. Memel then becomes a fairly successful city state, but lacks the important role as a regional entrepot that Hong Kong has after 1978 or Singapore turned into. Compared to its Communist neighbors though, it is a paradise though.
After Communism collapses, the large population of Poles, Balts, and others in Memel are able to assist their colleagues in recovering from Communism. At this point in time, it uses its existing networks to become a regional hub for trade, but mainly services, finance, and managerial expertise and technology transfer to local new Polish and Baltic businesses. It becomes the financial capital of the eastern Baltic after 1989, and as the former Communist countries develop, a major European financial center.
Memel's rise doesn't happen until the 1990s and later though unlike Hong Kong. It does become an important regional center of trade, but not an important world center.
