I think you will find this interesting. Now what's more interesting is that in this manuscript even the word chaklong is not there. There is one more (Nang Hum Fa) manuscript for which the copyist (Junaram?) gave its supposed Assamese translation too and it supposedly tells the story of first ever 'Chaklong marriage' but I haven't verified it myself

Regarding the word Chaklong or Choklong I can understand 𑜎𑜥𑜂𑜫: lóng (down) but I am not really sure Chak or Chok is the correct word. In Tai Dam tradition, there are two types of marriage - Dong Khuen ꪚꪮꪉ‌ꪄꪳ꫁ꪙ (up marriage - ดองขึ้น) where Boy moves to the Girl's family and Dong Long ꪚꪮꪉ‌ꪶꪩꪉ (down marriage - ดองลง) where the Girl moves to the Boy's family. Dong ꪚꪮꪉ‌ (ดอง) is an old Tai word for marriage which is only used by few Tai groups today like the Tai Dam. Even if it is indeed written as Chaklong or Choklong in manuscripts, I still don't think Chak or Chok is Ahom word but rather from some tribal language (since Assam is a graveyard of indigenous languages, it is difficult to say which one maybe Mawran) In Thai Chok ชก means to punch so choklong ชกลง means 'punch down' which obviously doesn't make sense in our context

As for your question on rituals, I will write a detailed article on it soon but concepts like Satidhora where Bridegroom's friend holds Umbrella for him to protect from heat and Juron where Bridegroom's family come to the Girl's family with lot of gifts and money to show that they are financially capable of taking care of the girl, all these rituals are unmistakeably Dai in origin!