The past and present tenses of "read" are spelt the same but have different pronunciation. This question is related to the post Why are the past and present tenses of "read" spelt the same?.
The second basic form of "to read" keeps the a to differentiate it from "red", the colour.
Your use of the term conjugation is very unclear. A conjugation is a table of all the forms a verb can take. All finite forms in active and passive and all infinite forms.
Some people apparently pronounce the past tense of the word beat as /bɛt/ ("bet"); see the following question: How common is pronouncing the past tense of beat as /bet/?
The standard spelling for both the present and the past tense is "beat"—as far as I know, this doesn't change for people who use the pronunciation /bɛt/ for the past tense.
The existence of accents that use the pronunciation /bɛt/ for the past tense of beat does not seem to be widely known among speakers who use the pronunciation /biːt/ for both past and present tense.
Tetsujin's answer to the ELL question "Can I say 'I sleeped all night' instead of slept?" mentions the word treat; apparently, this has a past-tense form /trɛt/ for some speakers, although its usual spelling is unclear to me. Tetsujin writes that "Northern Br Eng still uses 'treat' [pronounced tret] as the past tense, even though Southern Br Eng would use 'treated' [tree-ted]", but the OED entry for treat seems to indicate that the spelling "tret" has been used for this verb form ("15–16 Sc. treat, 15– Sc. and northern dialect tret").