I don't understand "blind thomas" part of your question. No one, to my knowledge, was blind, either Dylan Thomas or his father, D. J.
The poem is a villanelle dedicated to his father. It was most likely written when his father was ill in the mid 1940s, but it was published in 1952 after his father's death. Ironically, the poet lived only another year. He died of complications from pneumonia and swelling of the brain due to excessive alcohol.
The villanelle is very structured and difficult to write. It has 19 lines (5 tercets and a quatrain that ends with a couplet). It is a musical type of poetry that has refrains interwoven, and with a Welsh lilt (like Thomas'), it must have been a beautiful listening experience.
The villanelle affirms life, to the last breath. It is a "carpe diem" (seize the day) poem. Most "carpe diem" poems are applied to youth and love; here, Thomas applies it to old age and death, but he maintains the youthful and angry tone. There is a unity to the poem, literally and thematically. Life and death are united; youth and old age are united; as are night and day, gentleness and rage, sight and blindness.
The poem is paradoxical in that it is a plea to rage against death as a means of affirming life. In a way, the poem's philosophy is similar to that of the absurd hero of which Camus writes in "Myth of Sisyphus." Sisyphus hated death, loved life, and scorned the gods. He cheated Hades, tricked him into living two lives instead of one. He was willing to accept a life of absurd labor for the sake of seizing the day.