The entire application has to be in English of course. I guess best way is, if you really want to go to Singapore, to apply there directly (this is true for the most other Singaporean Companies, too and thus, you always should give ti a try). I myself applied with DEBIS "Go Global" program first, and after a successful application process I got forwarded and recommended to the Singaporean office. You should be ready for a phone interview in English, maybe in the local office language and expect questions corresponding to the typical personal, psychological ones related to your CV (strength and weaknesses...). This is especially the case if you try it via Go Global. But I can not tell you whether it would be a real advantage to go via Go Global although it was o.k. for me.