4. Dutch ties.
In 1954, Suriname became one of the constituent countries of the Kingdom of the Netherlands.
On 25 November 1975, it left the Kingdom to become an independent state.
In contrast to Indonesia's earlier war for independence from the Netherlands, the path toward Suriname's independence was an initiative of the then left-wing Dutch government.
Suriname continues to maintain close diplomatic, economic, and cultural ties with the Netherlands.
@ angel, that might be the reason for Dutch being their official language.