Prime Minister Lee Hsien Loong says Temasek Holdings' investment in Thailand is their commercial decision.
He says relations between Singapore and Thailand remain strong.
Mr Lee was asked to comment on the protests in Thailand against the Temasek-Shin Corp deal.
Mr Lee says: "We encourage them to go regional, we encourage them to take long-term stakes in our neighbours because we have confidence in Southeast Asia and our neighbours, and so does Temasek.
"But they make their own commercial decisions and when they go in they have to comply with the laws and all the rules of the countries which they go into.
"Just like when foreign companies invest in Singapore, we expect them to comply with all our laws and rules. We have very good relations with Thailand which we would like to develop and prosper in all fields."