The correct answer is - Cambodia.
In Indonesia the agriculture comes on shared second spot with 14%, in Cambodia it is the third with 23%, in the Philippines it is also third with 10%, while in Thailand also being third but with only 9%.
Despite not being the biggest contributor to the GDP, the agriculture in Cambodia is still responsible for almost one quarter of it. If we take into account that it is by far the most profitable natural income in the country, it just makes the agriculture even more important in this poor Southeast Asian nation.