Can a Turkish Sunni Muslim convert into Hindu and any other religion at his wish?
There is a hadith forbidding to change religion of a Muslim to any other religion and this hadith states that this kind of act is punishable by death.
Turkey is a laic country, nobody can kill you for that. Also most people in Turkey doesn't care. Even claiming to be an atheist is very cool among some teenager groups (stupid in most of them).
I am not a scholar at first, just interested in what questions arise in the ummah. First of all, I don't think there is a way to convert back to 'Hinduism', you need to be more specific in what you are asking.
Why would someone convert to Hinduism when Islam gives you peace and direct. While, Hinduism has so many rules and regulations that don't make much sense on why you are instructed to do so and it's not beneficial to you.
And As Always "Allahu 'Alim".
Whatever right I have said was because of Allah (SWT) and whatever I have said wrong was because of me and Shaytaan.
~Wa aliakum Asalam.
Totally, Islam is a religion whish doesn't agree you or other Muslims to change their religions. In fact according to Islam, every muslim who convert from Islam to ... then he would be called as Mortad. Of course being Mortad has some conditions and cases which have mention in the reference below. (of course unfortunately that is not in English). Anyway as it stated in short, you are not allowed to convert your religion which is Islam and it doesnt seem to be permitted even if you wish to do that. because there should be a negative matter in the mind which made you being interested in wishing in the question. Then there is no difference if he is a Turkish muslim or etc. Reference: http://www.tebyan.net/newindex.aspx?pid=209666