Who is Zheng Yu Dong from the SEA group?
It is difficult to determine exactly which Zheng Yu Dong and which SEA group you are referring to.

However, having reviewed various news articles and websites, I believe you may be referring to the Zheng Yu Dong who lists himself as CEO of Maribank on LinkedIn[0]. This name also appears as CEO of Maribank on the website for the Monetary Authority of Singapore [1].

It appears that MariBank is owned by Sea Limited [2] (originally called Garena) [3]. I believe that Sea Limited is the Sea Group you are referring to.

It is not clear whether Zheng Yu Dong holds other positions within Sea Limited.

Does this answer your question?

[0] https://www.linkedin.com/in/zhengyudong/?originalSubdomain=sg
[1] https://eservices.mas.gov.sg/fid/institution/detail/248595-MARIBANK-SINGAPORE-PRIVATE-LIMITED
[2] https://www.straitstimes.com/business/banking/sea-opens-digital-bank-maribank-to-public-on-invite-only-basis
[3] https://en.wikipedia.org/wiki/Sea_Ltd