When a Noahide prays he certainly obtains reward as we learn from the Prophet Isaiah, "My abode shall be declared a house of prayer unto all the nations of the world" (Isa. 56:7).
Even though they are not commanded to engage in prayer, it is evident that a Noahide does fulfill a commandment whenever he prays. (Note: In the preface, it was stated that commandment is a translation of the Hebrew word, mitzvah, which also means connection with God.)
When a Noahide is pressed by personal emergency, he is definitely expected to pray to God. Such prayer demonstrates a basic belief in God, exhibiting trust that He alone gives sustenance, that He alone heals. One who does not pray to God in time of dire need demonstrates that he does not believe in Him but in other forces.
The question arises, if a Noahide prays merely in his thoughts will he merit reward or must he pray verbally? We must conclude that he would not be rewarded for mental prayer as it is not prayer performed in the proper manner. Since prayer is a bond between the physical being and a personal God, one must use physicality to create this bond, which means verbal prayer.
The Noahide's prayer should not consist solely of supplications but should also include praises to God.
The act and experience of praying to God (and it should be obvious that it is forbidden to pray to any being other than God) has limitless levels. Whether one supplicates God for his needs and wants, or for help in times of danger or stress, or engages in deep meditational prayer in order to elevate oneself spiritually, prayer is always a mystical experience, a communion with the infinite Creator of one's own soul. Through prayer, man can strip his consciousness from all materialism and physicality, divorcing himself from his animal nature, and become a totally spiritual being. Through prayer, one can attain a level close to that of prophecy.
And King David wrote, "Praise the Lord, all nations, extol Him all the peoples" (Ps. 117:1). This verse from Psalms refers specifically to the prayers of the Children of Noah.
"And the dove came to him at the time of evening and, behold, an olive leaf plucked in her mouth, so Noah knew that the waters had abated from upon the face of the earth. And he waited yet another seven days, and he sent forth the dove and she did not continue to return to him again" (Gen. 8:10‑12).
This dove with the olive branch in her beak is the universal symbol of peace. The Talmud teaches that the dove said, "Rather my food be bitter as the olive branch in the hand of the Holy One, blessed be He, than sweet as honey in the hand of flesh and blood" (Eruvin 18).
"Behold I will send you Elijah the Prophet before the coming of the great and awesome day of the Lord. And he will turn the heart of the fathers to the children and the heart of the children to the fathers" (Mal. 3:23,24).