Instead of listing on the Singapore Exchange (SGX) in its hometown of Singapore, the company chose to be floated on the New York Stock Exchange in 2017.
If the ADR is its only public listing that doesn’t make it automatically suitable for an ISA. It’s the underlying asset that must trade on a HMRC recognised exchange.
Seas underlying asset does not, therefore its eligibility is questionable.
The SEC filings don’t identify a listing for the ‘Ordinary A class’ on which the ADRs are based.
A scan of worldwide markets revealed no listing other than the ADR (which is listed on multiple exchanges but that’s not a factor as the ‘parent’ has to be found)