I and my partner are both students in a university. However, sometimes we would transgress in our relationship. Honestly, we wanted to get married through khitbah marriage to avoid continuing to sin. We have thought things through and we think the best solution for us is to get married. The issue here is that if we get married without the knowledge of my girlfriend’s father and elope to Thailand, is our marriage valid? We would like to take this step to avoid any opposition from both of our families.
I will divide the answer to your question into two main points; (i) khitbah marriage (eloping to Thailand). First, the term khitbah marriage doesn’t exist in Islam. If the marriage is performed fulfilling all the conditions and requisites, then it is a valid marriage in Islam. Maybe the term khitbah marriage means a marriage where the married couple doesn’t live together in the same house for a period of the agreed time. In other words, the solemnization is held first but the wedding reception is held afterwards.
If this is what is meant by the questioner, the khitbah marriage is permissible for the reception and extravagant wedding gifts isn’t included as the requirements or conditions of marriage. Wedding reception and feast held inviting family and friends to celebrate the union of the couple is just a sunnah. As for the wedding gifts, they are just that, gifts from the groom to the bride. It is a sincere gift and not an obligation.
There are several factors as to why some people in our society chose khitbah marriage. Among them is the financial factor and for those who are students. Although they may not live together in the same house, the responsibilities of both the husband and wife should be fulfilled. However, it is best to discuss with the parents of both parties to avoid any issues in the future. Marriage isn’t just a way to channel one’s desires through halal means, rather it is a pure relationship that unites two people, souls and families.
The Prophet PBUH said:
رِضَى الرَّبِّ فِي رِضَى الوَالِدِ ، وَسَخَطُ الرَّبِّ فِي سَخَطِ الْوَالِدِ.
“The pleasure of the Lord lies in the pleasure of the parent. The anger of the Lord lies in the anger of the parent.” 
Regarding eloping, the 52nd National Muzakarah Fatwa Committee for Religious Affairs Malaysia which convened on 1st July 2002 have discussed the issue of Eloping to the South of Thailand. The Muzakarah has decided that marriage done overseas is valid on the condition that it fulfils the requisites and conditions of marriage and that the marriage is more than two marhalah, there is no court ruling in her place of residence based on syarak which prevented the woman from marrying. The marriage is also performed by a court-appointed wali that is acknowledged by the district of the country and the solemnization is done in the said district. 
The 52nd National Muzakarah Fatwa Committee for Religious Affairs Malaysia which convened on 1st July 2002 also discussed the issue of Eloping Leaving Her Wali More Than Two Marhalah According to Madhhab Al-Syafie. The Muzakarah has decided that a solemnization performed by an acknowledged person by the religious authorities for a couple who is more than two marhalah from her wali is valid according to madhhab Al-Syafie. 
It is advised that for couples who wanted to elope overseas, for instance, to Thailand for any reason which includes not getting the permission of the wali or wife’s permission for polygamy to first get the permission to marry overseas from their own respective State Religious Office. This involves several steps such as attending a pre-marital course, getting the polygamy permission letter if one didn’t get the permission of his wife, presenting a self-status statement (single/widowed) and others. If they marry in Thailand after getting the overseas marriage permission, the process of registering the Thailand marriage in Malaysia will be easier after their return from Thailand later.
I would like to remind you that marriage is not a light matter to be considered. Together with it are heavy responsibilities for both the husband and wife as the slaves of Allah. May Allah SWT ease the affairs of those who want to marry and strengthen the relationship of both families under the blessings of Allah SWT and their parents. Wallahua’lam.
 Narrated by al-Tirmizi (194)