It's not easy to answer the question, as all of the places suffer from deforestation.
For example, Borneo, an island shared by Indonesia and Malaysia ( and Brunei) is suffering a great deforestation on both the Indonesian and the Malaysian side.
However, from all the choices I would go for Malaysia, as it is undergoing deforestation at the fastest rate among the mentioned countries.
It used to once be completely covered by a forest, but in the last 50 years, almost half of that forest dissappeared (typically to make place for palm farms)