All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
The Islamic greeting is "As-salaamu 'Alaykum…" writing it abbreviated consists of many prohibitions some of them are as follows:
It is an innovation; when the Prophet wrote a letter to Heraclius, he wrote: "As-salaamu 'Alaa manittaba' al-Huda" (peace be upon those who follow the Guidance)." The Prophet did not write the abbreviations. The Prophet said: “Whoever innovates anything in this matter of ours that is not part of it, will have it rejected.” [Al-Bukhari and Muslim]
The wording according to another narration is, “Whoever does any action that is not in accordance with this matter of ours (i.e., Sunnah), will have it rejected.”
Using the abbreviation "ASAK" leads to the desertion of the expression that is legislated in Islam.
One does not get the reward that he would get had he used the actual words of greeting. A Muslim has to search for what is better as far as the matter of reward is concerned. It is reported by Imam Ahmad and others that a man came to the Messenger of Allaah and said, "As-Salaam ‘Alaykum" and sat. The Prophet said, “He will have ten rewards.” Another man came and said, “As-Salaam 'Alaykum wa rahmatullaah” and sat. The Prophet said, “He will have twenty rewards.” Then another man came and said, “As-Salaam ‘Alaykum wa rahmatullaahi wa barakaatuhu”, and sat there. The Prophet said, “He will have thirty rewards.”
The narration proves that the more the words of greeting are complete and perfect the higher and greater is the reward.
Actually by greeting one is supplicating for the person whom one meets. This purpose could not be achieved by the use of abbreviations; perhaps the greeted person may not pay any attention to such words, etc.
Muslim scholars dislike using abbreviations in place of the words of invoking blessing on the Prophet . The matter of greeting is also like the invocation of the blessings on the Prophet .
Qur'aanic style and Islamic teachings reject using the abbreviation "ASAK". So, it should be avoided.
Allaah knows best.