Nikah Bawah Tangan
A type of "hand fasting"
Nikah dibawah tangan means you will marry your spouse with a religious ceremony, but without having KUA (Religious affairs office) register your marriage and give the buku nikah (marriage book). This can be done with some Islamic requirements which are:
1. There is Wali (the male family member of the bride) as someone who will be giving your bride's hands to you e.g., her father or her brother or her father's brother (but not her mother's brother), or her father's father.
2. The witnesses (2 or 4 muslim men)
3. The dowry for your wife to be (the amount is up to her and the dowry is only for her, not the family). Yet if you'd like to give some appreciation or love token for her family, that is your choice but you must remember that is not considered as 'the dowry'.
4. Say the wedding oath in front of witnesses
If there is the moslem religious leader (Ustadz, or Imam) present at the ceremony to conduct the oath ceremony (if with KUA, this person is called Penghulu), it would be better but if there isn't, her father will be enough.
This type of islamic marriage is legal religiously (sah) but this is quite weak in the eye of civil law because there is no paper whatsoever registered at KUA, not to mention at Civil Registry office. BUT you can surely re-marry her legally in another country or in a civil ceremony after this. The important thing for Islamic families is that you don't just take her away illegally from their Islamic regulations because as a Muslim, marrying a non-Muslim or marrying without the aforementioned religious ceremony means that person is committing fornication.
Thanks to Aya from the Expat Forum for sharing her knowledge of this "alternative marriage" method.