Can someone help forward me the link for the check list of documents required for applying PR. And when is the deadline?

My father has recently granted a Thai citizenship based on the marriage with a Thai birth woman and I've been following him and living in Thailand for 20 years. At first I thought I don't have to go through the naturalisation process and can go straight apply for the Thai citizenship because of case decent. But I was advised that they won't accept because my father was not originally Thai birth in Thai soil, and I will have to apply on my own merit. So I need to know what paperwork I have to prepare and how many days I left for my submission.

Actually it doesn't matter where you are born in the world, if you are born to a Thai father or mother, you are Thai. The problem with your case is not that your father was not born in Thailand but that he was not Thai at the time of your birth. Children under 20 can apply for naturalisation along with their parents but you were obviously too old for that at the time.

You have till 31 Dec to apply for PR.

Is there a literacy or language requirement for residency?

No reading or writing required but you must be able to speak enough Thai to pass a panel interview as well talk to the officers handling your application. Intermediate Thai is required but not total fluency.