According to the Ramayana, Dasharatha had 3 wives, but in some books they say he had 60,000 wives. Which one is true?
The claim of Dasharatha having 60,000 wives is from later versions of the Ramayana, particularly the Kamba Ramayana. But as far as the Valmiki Ramayana goes, Dasharatha has at least 350 wives, as described in the Ayodhya Kanda of the Ramayana:
That king Dasaratha, who speaks truth, whose mind is virtuous, who is like an ocean by his depth of character and who is blemish less like a sky, replied to Sumantra as follows: "Oh, Sumantra! bring all my wives, who are here. Surrounded by all of them, I want to see the virtuous Rama." Sumantra, after entering the gynaecium, spoke these words to those women as follows: "Oh, the venerable ladies! The king is calling you. Go there without delay." All those women, asked thus by Sumantra as per the king's orders, went to his palace, after knowing the instructions of their husband. Encircling Kausalya, three hundred fifty women, steadfast in their vow (of devotion to their husband), with their eyes reddened, went there slowly.
Note that he tells his minister Sumantra to bring the wives "who are here", so it's possible that Dasaratha had more wives who happened to not be present in the gynaecium [place for women].
In any case, it's still true that he only had three queens, Kausalya, Kaikeyii, and Sumitra.
It is also stated that he married them because of Parashu Rama’s vow to kill the Kshatriyas as a revenge for his father’s death.
however the was one exception, that he will not kill a Kshatriya, who had Marriage Kangan on his wrist.
This Kangan, yellow band of Thread was used to be worn for one year from the date of marriage.
Convinced that he could not beat Parashurama, Dasaratha married ne woman a Year to escape the wrath of Parashurama.
What does Valimiki Ramayana say on this?
Valmiki Ramayana, Ayodhya Kanda, Chapter 34, Verses 10 to 13:
Dasharatha summons Sumantra to fetch all his wives when Rama was ready to to go to forest.
Sumantra, after entering the gynaecium, spoke these words to those women as follows: “Oh, the venerable ladies! The king is calling you. Go there without delay. All those women, asked thus by Sumantra as per the king’s orders, went to his palace, after knowing the instructions of their husband.’
Valmiki Ramayana, Ayodhya Kanda, Chapter 34, Verse 10
Dasaratha said to Sumantra, “Oh, Sumantra! being all my wives, who are here. Surrounded by all of them, I want to see the virtuous Rama.” (‘who are here’ means available at the capital city then)
Valmiki Ramayana, Ayodhya Kanda, Chapter 34, Verse 13:
अर्ध सप्त शताः ताः तु प्रमदाः ताम्र लोचनाः |
कौसल्याम् परिवार्य अथ शनैः जग्मुर् धृत व्रताः || २-३४-१३
“ardha sapta shataah taah tu pramadaah taamra locanaah | kausalyaam parivaarya atha shanaih jagmur dhrita vrataah ||” 2-34-13
‘Encircling Kausalya, three hundred fifty women, steadfast in their vow (of devotion to their husband), with their eyes reddened, went there slowly.’
Valmiki Ramayana, Book II : Ayodhya Kanda, Chapter (Sarga) 39, Verse 34 & 35:
Rama said to Queen Kausalya, His mother,
“Oh, mother! You do not grieve. You look after my father. The end of exile will come rather soon.” “Fourteen years will elapse, while you are asleep. you as such, will see me, duly arrived here in my entire being, surrounded by my well-wishers.”
Valmiki Ramayana, Book II : Ayodhya Kanda, Chapter (Sarga) 39, Verse 36:
एतावद् अभिनीत अर्थम् उक्त्वा स जननीम् वचः |
त्रयः शत शत अर्धा हि ददर्श अवेक्ष्य मातरः || २-३९-३६
etaavad abhiniita artham uktvaa sa jananiim vacah |
trayah shata shata ardhaa hi dadarsha avekshya maatarah || 2-39-36
Uttering the aforesaid words of such quality and appropriate meaning to his mother, Rama thought once again and gazed at his three hundred and fifty step-mothers.
Valmiki Ramayana, Book II : Ayodhya Kanda, Chapter (Sarga) 39, Verses 37 to 40:
Rama joined his palms and saluted those step mothers also, who were too distressed in the same way and spoke these words which were in consonance with the spirit of righteousness.
“Please excuse me, if I have done any mistake either becuase of our living together or due to ignorance on my part. I now take leave of you all.” All those women, whose mind was overpowered with grief, heard the aforesaid cool submission of Rama, which was in consonance with righteousness. While Rama was speaking thus, an outery, resembling the wail of female cranes arose from those wives of Dasaratha