सीतानाथ समारम्भां रामानन्दार्य मध्यमाम्।
अस्मदाचार्य पर्यन्तां वन्दे श्रीगुरू परम्पराम् ।।

This chaupāai of Śrīmad Rāmāyaṇa has a very depth meaning in it, let's see how!!

बंदउँ कौसल्या दिसि प्राची। कीरति जासु सकल जग माची।।

प्रगटेउ जहँ रघुपति ससि चारू। बिस्व सुखद खल कमल तुसारू।।

I bow before mother Kaushalya who symbolizes the eastern horizon (पूर्व दिशा). Her fame and good name has spread over the whole world (as the mother of Lord Ram). For she gave birth to Lord Ram who is like the beautiful full moon that gives peace, comfort, joy and happiness to the world at large, and also causes the lotus representing the evil and the wicked to shrivel up and close its petals as if bitten by frost.

This chaupāai was directly translated from;

श्रीकोशलेन्द्रदयिता राममाता यशस्विनी प्राध्या सा वन्दनीया मे कीर्त्तिर्यस्यास्ति विश्रुता रामचन्द्रमसं चारु प्रादुर्भूतं सनातनम्।
खलाब्जे हिमवद्धाति साधूनां सुखदायकम् कौशल्यायै नमस्यामि यथा पूर्वा दिगुत्तमा। प्रादुर्भावो बभौ रामः शीतांशुः सर्वसौख्यदः ॥

(Shiv Samhitā, 4.5.23–24 & Sri Ascharya Rāmāyaṇa)

Kausalyā Disi Prāchi (कौसल्या दिसि प्राची) :~

Moon's dwitiya ( द्वितीय) is very auspicious, it is worshiped by all; But this moon is phase less (कलाहीन), rises in the west (पश्चिम) and is dependent on others.

By saying the east direction in the chaupāai, Śrī Tulsidas ji informed about the full moon which rises with its complete sixteen Kala, similarly Shri Ram Ji Maharāj is also complete with 16 Kala, Shodash Kalā Avatār.

Similarly, in Shrimad Bhagwat, the birth of Shri Krishna has been told from the east direction symbolising mother Devaki.

देवक्यां देवरूपिण्यां विष्णु: सर्वगुहाशय: ।
आविरासीद् यथा प्राच्यां दिशीन्दुरिव पुष्कल: ॥

ŚB 10.3.7-8

Then the Supreme Personality of Godhead, Viṣṇu, who is situated in the core of everyone’s heart, appeared from the womb of Devakī in the dense darkness of night, like the full moon rising on the eastern horizon.

That is, as the full moon appears in the east, in the same way, Śrī Hari Vishnu appeared from the womb of Devaki Ji.

Goswami Ji in chaupāai says that the appearance of 'Raghupathi Sasi' explains that the one whose name is 'Raghunath' has appeared himself. Not like in Sri Krishna Avatār where Śrī Hari Vishnu appeared first as Vishnu than he took up Śrī Krishna form. Rather here the lord HIMSELF appeared in his original form as Śrī Rām is not an incarnation of lord Vishnu according to Rāmayan and Vedās.

As according to Rāmāyana;

ततस्त्वमसि दुर्धर्षात्तस्माद् भावात् सनातनात् । रक्षार्थं सर्वभूतानां विष्णुत्वं उपजग्मिवान् ॥

(Śrī Vālmiki Rāmāyaṇa 7.104.9)

"After my prayers in the begining of the creation, Oh Rāma ! You forsaken Your durdharsa (the swarupa which is difficult to be achieved for many i.e. the eternal two armed Śrī Rāma form) and assumed the form of Vīshnu for the sake of protection and sustenance of all the beings."

नेति नेति जेहि बेद निरूपा। निजानंद निरुपाधि अनूपा॥
संभु बिरंचि बिष्नु भगवाना। उपजहिं जासु अंस तें नाना॥

(ŚrīRāmacaritamānasa 1.143.3)

Meaning :- Whom the Vedas describe by saying 'neti-neti' (not this, not this also). Who is blissful, titleless and unique and from whose part many Lord Shiva, Brahma and Vishnu appear (He is Sri Rām).

According to Nārad Panchrātra;

वासुदेवादि मुर्तिनाम् चतुर्नाम् कारणं परम्।
चतुर्विंशति मुर्तिनाम् आश्रय श्रीरामः शरणं मम।।

(Brihād Brahmā Samhitā 2.7.8)

Śrī Hari Nārāyan says to Brahmā, The supreme cause of the four vyuhas, such as Vāsudeva etc. Śrī Rāma, the shelter of the twenty-four avtars, is my refuge.

परान्नारायणाच्चापि कृष्णात्परतरादपि।
यो वै परतमः श्रीमान् रामो दाशरथिः स्वराट् ॥

(Vashistha Samhita, Chapter 26, verse 17)

The one who is beyond Śrī Hāri Nāräyana, who is beyond even Śrī Krishnā, who is the most Paratammamvarat Paramatma, that is Dashrath's son Raghavā.

नारायण सहस्राणि कृष्णाद्याः शत कोटयः ।
कोटि कोटयवताराश्च जाता रामांघ्रि पंकजात् ॥

(Shiv Samhita, Patala 5, chap. 2, verse 39)

The incarnations of thousands of Narayans and hundreds of crores of Shri Krishna etc. continue to take place by the lines of the feet of Shri Raghunandan.

According to Vedās;

वायुपुत्रं विघ्नेशं वाणीं दुर्गां क्षेत्रपालकं सूर्यं चन्द्रं नारायणं नारसिंहं वासुदेवं वाराहं तत्सर्वान्त्समात्रान्त्सीतं लक्ष्मणं शत्रुघ्नं भरतं विभीषणं सुग्रीवमङ्गदं जाम्बवन्तं प्रणवमेतानि रामस्याङ्गानि जानीथाः ।

(Yajurvedā Shäkhayam RāmRahāshyopanishād 1.7½)

I myself (Sri Hanuman Ji), Śrī Ganēshā, Goddess Saraswati, Goddess Durgā, All the Guardian (Khetra Pāl), Sun (Suryā), Moon, Lord Śrī Hari Narayan, Lord Narasimha, Lord Vāsudev (Śrī Krishnā), Lord Vāraha etc. All are the mere parts of Lord Śrī Rāma. Lakshmāna, Shātrughna, Bharata, Vibhishana, Sugriva, Angad, Jambavant and Pranav (Om ॐ) are also parts of Lord Śrī Rāma.

यस्यांशेन एव ब्रह्म विष्णु महेश्वरा अपि जाता महाविष्णुर्य्यस्य दिव्यगुणाश्च । स एव कार्यकारणयोः परः परमपुरुषो रामो दाशरथिर्वभुव॥

(Atharvavedā Shakha Vedsaropanishad, Uttarkhand)

From whose Portions (Ansh) Brahma, Visnu and Mahesvara are manifested, Whose divine Guna is Mahavisnu, The only one who is the cause of all causes, The one who is higher than the highest, such is Śrī Rāma, the son of Dasratha. (Approx same shloka is also found in Vashisht Samhita Ch. 26 and Samved Sudarshan Samhita 1–5.)

Same like that in Valmiki Ramayan Śrī Rām has appeared in his original form not as an Avatār of Sri Hari Vishnu;

प्रोद्यमाने जगन्नाथं सर्वलोकनमस्कृतम्।कौसल्याऽजनयद्रामं सर्वलक्षणसंयुतम्।।

(Sri Vālmīki Rāmayan 1.18.10)

Kausalya gave birth to Rām (here one should not that Lord Rama appeared with two arms not with four arms as in the case of Krishna avatar), who is the Lord of the entire universe (जगन्नाथ) who received obeisance from all the worlds and was adorned with all auspicious signs.

In that chaupāai प्रगटेउ जहँ रघुपति ससि चारू। Sri Tulsidās Ji has cleared that original form of godhead Śrī Rām appeared himself not anyone's incarnation. But yes! Sri Vishnu takes Sri Ram avatār to teach the character of Shri Ram to the worldly people, this story is famous in Purana not in Ramayan and Vedās.

Please Chant SitaRam SitaRam SitaRam

Glory to Śrīmad Goswami Tulsidas Ji

Glory to Ānand Bhāshyakār Śrīmad Jagādgurü Ramānandacharya