this is a correct account of the ID situation, very common in thaland among the older people.
nowadays, when an initial birth registration is done, if only a year available, usually taken from the house paper, january 1st is just inserted, my daughter in law's case on this aspect.
my wife, born 1948, the ID only shows the year, hence, also her thai passport.
she has travelled the world extensively with little problen, save the explanation here.
her passport however will not work in the thai exit & reentry machines.
she only has to go stand in line with me. always no problem.
at some banks, they often get upset about this for their papperwork, but finally accept it.
she married me in canada 43 years ago, and got a cdn passport, although with my last name.
I gave her a birth date for it, so that travel document works fine.
she now has 2 passports, each with different information, name, dates.
we have also tried to fix it over the years, but it is true that no retroactive changes can or will be made in thailand.
new info. only, such as name change or married name.